The Experts below are selected from a list of 573 Experts worldwide ranked by ideXlab platform

Norbert Sewald - One of the best experts on this subject based on the ideXlab platform.

  • Novel unit B Cryptophycin analogues as payloads for targeted therapy.
    Beilstein journal of organic chemistry, 2018
    Co-Authors: Eduard Figueras, Adina Borbély, Mohamed F. Ismail, Marcel Frese, Norbert Sewald
    Abstract:

    Cryptophycins are naturally occurring cytotoxins with great potential for chemotherapy. Since targeted therapy provides new perspectives for treatment of cancer, new potent analogues of cytotoxic agents containing functional groups for conjugation to homing devices are required. We describe the design, synthesis and biological evaluation of three new unit B Cryptophycin analogues. The O-methyl group of the unit B D-tyrosine analogue was replaced by an O-(allyloxyethyl) moiety, an O-(hydroxyethyl) group, or an O-(((azidoethoxy)ethoxy)ethoyxethyl) substituent. While the former two maintain cytotoxicity in the subnanomolar range, the attachment of the triethylene glycol spacer with a terminal azide results in a complete loss of activity. Docking studies of the novel Cryptophycin analogues to β-tubulin provided a rationale for the observed cytotoxicities.

  • Cryptophycins: cytotoxic cyclodepsipeptides with potential for tumor targeting
    Journal of peptide science : an official publication of the European Peptide Society, 2017
    Co-Authors: Christine Weiß, Eduard Figueras, Adina Borbély, Norbert Sewald
    Abstract:

    Cryptophycins are a class of 16-membered highly cytotoxic macrocyclic depsipeptides isolated from cyanobacteria. The biological activity is based on their ability to interact with tubulin. They interfere with microtubule dynamics and prevent microtubules from forming correct mitotic spindles, which causes cell-cycle arrest and apoptosis. Their strong antiproliferative activities with 100-fold to 1000-fold potency compared with those of paclitaxel and vinblastine have been observed. Cryptophycins are highly promising drug candidates, as their biological activity is not negatively affected by P-glycoprotein, a drug efflux system commonly found in multidrug-resistant cancer cell lines and solid tumors. Cryptophycin-52 had been investigated in phase II clinical trials but failed because of its high neurotoxicity. Recently, Cryptophycin conjugates with peptides and antibodies have been developed for targeted delivery in tumor therapy. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.

  • Conjugates of Modified Cryptophycins and RGD-Peptides Enter Target Cells by Endocytosis
    2016
    Co-Authors: Markus Nahrwold, Christine Weiß, Tobias Bogner, Felix Mertink, Jens Conradi, Benedikt Sammet, Ralf Palmisano, Soledad Royo Gracia, Thomas Preuße, Norbert Sewald
    Abstract:

    Tumor targeting anticancer drug conjugates that contain a tumor recognition motif (homing device) are of high current relevance. Cryptophycins, naturally occurring cytotoxic cyclo-depsipeptides, have been modified by total synthesis to provide analogues suitable for conjugation to peptide-based homing devices. An array of functionalized β2-amino acids was synthesized and incorporated into Cryptophycins. All analogues proved to be highly active in the cytotoxicity assay using the human cervix carcinoma cell line KB-3-1 and its multidrug-resistant subclone KB-V1. Conformational analysis of Cryptophycin-52 and two synthetic analogues was performed by NMR and MD methods to obtain information on the influence of the unit C configuration on the overall conformation. An azide-functionalized Cryptophycin was connected by CuAAC to an alkyne-containing fluorescently labeled cyclic RGD-peptide as the homing device for internalization studies. Confocal fluorescence microscopy proved integrin-mediated internalization by endocytosis and final lysosomal localization of the Cryptophycin prodrug

  • Conjugates of modified Cryptophycins and RGD-peptides enter target cells by endocytosis.
    Journal of medicinal chemistry, 2013
    Co-Authors: Markus Nahrwold, Christine Weiß, Tobias Bogner, Felix Mertink, Jens Conradi, Benedikt Sammet, Ralf Palmisano, Soledad Royo Gracia, Thomas Preuße, Norbert Sewald
    Abstract:

    Tumor targeting anticancer drug conjugates that contain a tumor recognition motif (homing device) are of high current relevance. Cryptophycins, naturally occurring cytotoxic cyclo-depsipeptides, have been modified by total synthesis to provide analogues suitable for conjugation to peptide-based homing devices. An array of functionalized β(2)-amino acids was synthesized and incorporated into Cryptophycins. All analogues proved to be highly active in the cytotoxicity assay using the human cervix carcinoma cell line KB-3-1 and its multidrug-resistant subclone KB-V1. Conformational analysis of Cryptophycin-52 and two synthetic analogues was performed by NMR and MD methods to obtain information on the influence of the unit C configuration on the overall conformation. An azide-functionalized Cryptophycin was connected by CuAAC to an alkyne-containing fluorescently labeled cyclic RGD-peptide as the homing device for internalization studies. Confocal fluorescence microscopy proved integrin-mediated internalization by endocytosis and final lysosomal localization of the Cryptophycin prodrug.

  • Recent approaches for the synthesis of modified Cryptophycins
    Natural product reports, 2013
    Co-Authors: Christine Weiß, Benedikt Sammet, Norbert Sewald
    Abstract:

    Covering: 2005 to 2013Cryptophycins are a family of antimitotic depsipeptides with very high cytotoxicity even against multi-drug resistant (MDR) cancer cells. The first representative was isolated from cyanobacteria Nostoc sp. in 1990. Their bioactivity is based on their interaction with the protein tubulin. Cryptophycins were found to induce apoptosis due to inhibition of the microtubule dynamics. Consequently, Cryptophycin analogues are considered as potential antitumour agents. Retrosynthetically, Cryptophycins can be subdivided into four building blocks, namely units A–D, to be assembled in the total synthesis. Since the discovery of this compound class, numerous synthetic analogues have been designed for structure–activity relationship (SAR) studies. This review gives a critical overview on Cryptophycins, while the main focus lies on the synthetic challenges of recently published Cryptophycins, together with emerging concepts on Cryptophycin bioconjugation and prodrug design.

Richard E. Moore - One of the best experts on this subject based on the ideXlab platform.

  • Biosynthetic characterization and chemoenzymatic assembly of the Cryptophycins. Potent anticancer agents from cyanobionts.
    ACS chemical biology, 2006
    Co-Authors: Nathan A. Magarvey, Richard E. Moore, Trimurtulu Golakoti, Yousong Ding, Zachary Q. Beck, Udo Huber, Thomas K. Hemscheidt, Dafna Abelson, David H. Sherman
    Abstract:

    The lichen cyanobacterial symbiont Nostoc sp. ATCC 53789 and its close relative Nostoc sp. GSV 224 are prolific producers of natural products, generating >25 derivatives of the Cryptophycin class of secondary metabolites. Cryptophycin 1, the prototypic member of the class, is a potent tubulin-depolymerizing agent, and several semisynthetic derivatives are being developed as anticancer therapeutics. Here we provide a detailed characterization of the Cryptophycin metabolic pathway by stable-isotope labeling experiments and through cloning, sequencing, and annotating the Cryptophycin biosynthetic gene cluster. A comparative secondary metabolomic analysis based on polyketide (PK)/non-ribosomal peptide gene clusters from the phylogenetically related, non-Cryptophycin producing cycad symbiont, Nostoc punctiforme ATCC 29133, was used to identify the Cryptophycin biosynthetic genes that encompass approximately 40 kb within the lichen symbiont Nostoc sp. ATCC 53789 genome. The pathway encodes a collinear set of enzymes, including three modular PK synthases, two non-ribosomal peptide synthetase modules, and an integrated adenylation/ketoreductase didomain for elaboration of the leucic acid subunit. In addition, genes encoding key tailoring steps, including a FAD-dependent halogenase and CYP450 epoxidase, were identified. The inherent flexibility of the Cryptophycin biosynthetic enzymes was harnessed to generate a suite of new analogues by altering the pool of PK starter units and selected amino acid extender groups. Characterization of the Cryptophycin CYP450 enabled development of the first stereospecific synthesis of Cryptophycin 2, through a tandem chemoenzymatic synthesis from the natural seco-Cryptophycin 4 chain elongation intermediate.

  • Cryptophycins-309, 249 and other Cryptophycin analogs: Preclinical efficacy studies with mouse and human tumors
    Investigational New Drugs, 2005
    Co-Authors: Jian Liang, Richard E. Moore, Eric D. Moher, John E. Munroe, Rima S. Al-awar, David A. Hay, David L. Varie, Tony Y. Zhang, James A. Aikins, Michael J. Martinelli
    Abstract:

    Cryptophycins-1 and 52 (epoxides) were discovered to have in-vitro and in-vivo antitumor activity in the early 1990s. The chlorohydrins of these, Cryptophycins-8 and 55 (also discovered in the early 1990s) were markedly more active, but could not be formulated as stable solutions. With no method to adequately stabilize the chlorohydrins at the time, Cryptophycin-52 (LY 355073) entered clinical trials, producing only marginal antitumor activity. Since that time, glycinate esters of the hydroxyl group of the chlorohydrins have been synthesized and found to provide stability. Three of the most active were compared herein. Cryptophycin-309 (C-309) is a glycinate ester of the chlorohydrin Cryptophycin-296. The glycinate derivative provided both chemical stability and improved aqueous solubility. After the examination of 81 different Cryptophycin analogs in tumor bearing animals, C-309 has emerged as superior to all others. The following %T/C and Log Kill (LK) values were obtained from a single course of IV treatment (Q2d × 5) against early staged SC transplantable tumors of mouse and human origin: Mam 17/Adr [a pgp (+) MDR tumor]: 0%T/C, 3.2 LK; Mam 16/C/Adr [a pgp (−) MDR tumor]: 0%T/C, 3.3 LK; Mam 16/C: 0%T/C, 3.8 LK; Colon 26: 0%T/C, 2.2 LK; Colon 51: 0%T/C, 2.4 LK; Pancreatic Ductal Adenocarcinoma 02 (Panc 02): 0%T/C, 2.4 LK; Human Colon HCT15 [a pgp (+) MDR tumor]: 0%T/C, 3.3 LK; Human Colon HCT116: 0%T/C, 4.1 LK. One additional analog, Cryptophycin-249 (C-249, the glycinate of Cryptophycin-8), also emerged with efficacy rivaling or superior to C-309. However, there was sufficient material for only a single C-249 trial in which a 4.0 LK was obtained against the multidrug resistant breast adenocarcinoma Mam-16/C/Adr. C-309 and C-249 are being considered as second-generation clinical candidates.

  • Isolation and structure determination of Cryptophycins 38, 326, and 327 from the terrestrial cyanobacterium Nostoc sp. GSV 224.
    Journal of natural products, 2004
    Co-Authors: Sreedhara Chaganty, Richard E. Moore, Trimurtulu Golakoti, Carl E. Heltzel, Wesley Y. Yoshida
    Abstract:

    Cryptophycin-38 (2), -326 (3), and -327 (4) are three new trace constituents of the terrestrial cyanobacterium Nostoc sp. GSV 224. Cryptophycin-38 is a stereoisomer of Cryptophycin-1 (1) and to date is the only naturally occurring analogue that possesses a S,S epoxide group in unit A. Cryptophycin-327 is a geometric isomer that differs from 1 in having a cis Delta(2)-double bond in unit A. Cryptophycin-326 is related to Cryptophycin-21, but has two chlorines ortho to the methoxy group in unit B. The relative and absolute stereochemistries of 2 have been related to known Cryptophycins by semisynthesis and/or spectral analysis.

  • a convergent approach to Cryptophycin 52 analogues synthesis and biological evaluation of a novel series of fragment a epoxides and chlorohydrins
    Journal of Medicinal Chemistry, 2003
    Co-Authors: Rima S Alawar, Richard E. Moore, Richard M Schultz, Sherri L Andis, Joseph H Kennedy, Jian Liang, Trimurtulu Golakoti, G V Subbaraju, Thomas H Corbett
    Abstract:

    Cryptophycin 52 is a synthetic derivative of Cryptophycin 1, a potent antimicrotubule agent isolated from cyanobacteria. In an effort to increase the potency and water solubility of the molecule, a structure-activity relationship study (SAR) was initiated around the phenyl ring of fragment A. These Cryptophycin 52 analogues were accessed using a Wittig olefination reaction between various triphenylphosphonium salts and a key intermediate aldehyde prepared from Cryptophycin 53. Substitution on the phenyl ring of fragment A was well tolerated, and several of these analogues were equally or more potent than Cryptophycin 52 when evaluated in vitro in the CCRF-CEM leukemia cell line and in vivo against a murine pancreatic adenocarcinoma.

  • Synthesis of Cryptophycin 52 using the sharpless asymmetric dihydroxylation: diol to epoxide transformation optimized for a base-sensitive substrate.
    The Journal of organic chemistry, 2000
    Co-Authors: Jian Liang, Richard E. Moore, Eric D. Moher, David W. Hoard
    Abstract:

    A synthesis of Cryptophycin 52 (2) is reported using a Sharpless asymmetric dihydroxylation (AD) strategy to install the epoxide moiety. The high stereoselectivity of the AD reaction that allows for an efficient means of preparing the epoxide is in contrast to the standard direct epoxidation of Cryptophycin substrates, which proceeds with poor diastereoselectivity. Methodology for conversion of the diol AD product to the requisite epoxide is disclosed. The transformation has been optimized to proceed in high yield in the presence of base sensitive functionality.

Sewald Norbert - One of the best experts on this subject based on the ideXlab platform.

  • Synthesis and Biological Characterization of Monomeric and Tetrameric RGD-Cryptophycin Conjugates.
    'Wiley', 2020
    Co-Authors: Borbély, Adina Noémi, Figueras Agustí Eduard, Thoreau Fabien, Kadri Malika, Coll Jean-luc, Boturyn Didier, Sewald Norbert
    Abstract:

    Borbély AN, Thoreau F, Figueras Agustí E, et al. Synthesis and Biological Characterization of Monomeric and Tetrameric RGD-Cryptophycin Conjugates. Chemistry - A European Journal. 2020;26(12):2602-2605.The effective delivery of cytotoxic agents to the tumor cells is a key challenge in anticancer therapy. Multivalent integrinspecific ligands are considered a promising tool to increase the binding affinity, selectivity, and internalization efficiency of small molecule-drug conjugates. Here we report the synthesis and biological evaluation of a multimeric conjugate containing the high-affinity integrin alpha v beta 3 binding ligand RAFT- c (RGDfK) 4 , a lysosomally cleavable Val-Cit linker and Cryptophycin-55 glycinate, a potent inhibitor of tubulin polymerization. In vitro cytotoxicity assays verified that the multimeric RGD-Cryptophycin conjugate displays improved potency compared to the monomeric analogue in integrin alpha v beta 3 overexpressing tumor cell lines, while significantly reduced activity was observed in the integrin-negative cell line. © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • Synthesis and Biological Characterization of Monomeric and Tetrameric RGD‐Cryptophycin Conjugates
    'Wiley', 2020
    Co-Authors: Borbély Adina, Thoreau Fabien, Kadri Malika, Coll Jean-luc, Boturyn Didier, Figueras Eduard, Sewald Norbert
    Abstract:

    International audienceThe effective delivery of cytotoxic agents to the tumor cells is a key challenge in anticancer therapy. Multivalent integrinspecific ligands are considered a promising tool to increase the binding affinity, selectivity, and internalization efficiency of small molecule-drug conjugates. Here we report the synthesis and biological evaluation of a multimeric conjugate containing the high-affinity integrin αvβ3binding ligand RAFT-c(RGDfK)4, a lysosomally cleavable Val-Cit linker and Cryptophycin-55 glycinate, a potent inhibitor of tubulin polymerization. In vitro cytotoxicity assays verified that the multimeric RGD-Cryptophycin conjugate displays improved potency compared to the monomeric analogue in integrin αvβ3overexpressing tumor cell lines, while significantly reduced activity was observed in the antigen-negative cell lin

  • Novel unit B Cryptophycin analogues as payloads for targeted therapy
    'Beilstein Institut', 2018
    Co-Authors: Figueras Agustí Eduard, Borbély, Adina Noémi, Ismail Mohamed, Frese Marcel, Sewald Norbert
    Abstract:

    Figueras Agustí E, Borbély AN, Ismail M, Frese M, Sewald N. Novel unit B Cryptophycin analogues as payloads for targeted therapy. Beilstein Journal of Organic Chemistry. 2018;14:1281-1286.Cryptophycins are naturally occurring cytotoxins with great potential for chemotherapy. Since targeted therapy provides new perspectives for treatment of cancer, new potent analogues of cytotoxic agents containing functional groups for conjugation to homing devices are required. We describe the design, synthesis and biological evaluation of three new unit B Cryptophycin analogues. The O-methyl group of the unit B D-tyrosine analogue was replaced by an O-(allyloxyethyl) moiety, an O-(hydroxyethyl) group, or an O-(((azidoethoxy) ethoxy) ethoyxethyl) substituent. While the former two maintain cytotoxicity in the subnanomolar range, the attachment of the triethylene glycol spacer with a terminal azide results in a complete loss of activity. Docking studies of the novel Cryptophycin analogues to beta-tubulin provided a rationale for the observed cytotoxicities

  • Cryptophycins: cytotoxic cyclodepsipeptides with potential for tumor targeting
    'Wiley', 2017
    Co-Authors: Weiss Christine, Figueras Agustí Eduard, Borbély, Adina Noémi, Sewald Norbert
    Abstract:

    Weiss C, Figueras Agustí E, Borbély AN, Sewald N. Cryptophycins: cytotoxic cyclodepsipeptides with potential for tumor targeting. Journal of Peptide Science. 2017;23(7-8):514-531.Cryptophycins are a class of 16-membered highly cytotoxic macrocyclic depsipeptides isolated from cyanobacteria. The biological activity is based on their ability to interact with tubulin. They interfere with microtubule dynamics and prevent microtubules from forming correct mitotic spindles, which causes cell-cycle arrest and apoptosis. Their strong antiproliferative activities with 100-fold to 1000-fold potency compared with those of paclitaxel and vinblastine have been observed. Cryptophycins are highly promising drug candidates, as their biological activity is not negatively affected by P-glycoprotein, a drug efflux system commonly found in multidrug-resistant cancer cell lines and solid tumors. Cryptophycin-52 had been investigated in phase II clinical trials but failed because of its high neurotoxicity. Recently, Cryptophycin conjugates with peptides and antibodies have been developed for targeted delivery in tumor therapy. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd

  • Recent approaches for the synthesis of modified Cryptophycins
    'Royal Society of Chemistry (RSC)', 2013
    Co-Authors: Weiss Christine, Sammet Benedikt, Sewald Norbert
    Abstract:

    Weiss C, Sammet B, Sewald N. Recent approaches for the synthesis of modified Cryptophycins. Natural Product Reports. 2013;30(7):924-940.Cryptophycins are a family of antimitotic depsipeptides with very high cytotoxicity even against multi-drug resistant (MDR) cancer cells. The first representative was isolated from cyanobacteria Nostoc sp. in 1990. Their bioactivity is based on their interaction with the protein tubulin. Cryptophycins were found to induce apoptosis due to inhibition of the microtubule dynamics. Consequently, Cryptophycin analogues are considered as potential antitumour agents. Retrosynthetically, Cryptophycins can be subdivided into four building blocks, namely units A-D, to be assembled in the total synthesis. Since the discovery of this compound class, numerous synthetic analogues have been designed for structure-activity relationship (SAR) studies. This review gives a critical overview on Cryptophycins, while the main focus lies on the synthetic challenges of recently published Cryptophycins, together with emerging concepts on Cryptophycin bioconjugation and prodrug design

Markus Nahrwold - One of the best experts on this subject based on the ideXlab platform.

  • Conjugates of Modified Cryptophycins and RGD-Peptides Enter Target Cells by Endocytosis
    2016
    Co-Authors: Markus Nahrwold, Christine Weiß, Tobias Bogner, Felix Mertink, Jens Conradi, Benedikt Sammet, Ralf Palmisano, Soledad Royo Gracia, Thomas Preuße, Norbert Sewald
    Abstract:

    Tumor targeting anticancer drug conjugates that contain a tumor recognition motif (homing device) are of high current relevance. Cryptophycins, naturally occurring cytotoxic cyclo-depsipeptides, have been modified by total synthesis to provide analogues suitable for conjugation to peptide-based homing devices. An array of functionalized β2-amino acids was synthesized and incorporated into Cryptophycins. All analogues proved to be highly active in the cytotoxicity assay using the human cervix carcinoma cell line KB-3-1 and its multidrug-resistant subclone KB-V1. Conformational analysis of Cryptophycin-52 and two synthetic analogues was performed by NMR and MD methods to obtain information on the influence of the unit C configuration on the overall conformation. An azide-functionalized Cryptophycin was connected by CuAAC to an alkyne-containing fluorescently labeled cyclic RGD-peptide as the homing device for internalization studies. Confocal fluorescence microscopy proved integrin-mediated internalization by endocytosis and final lysosomal localization of the Cryptophycin prodrug

  • Conjugates of modified Cryptophycins and RGD-peptides enter target cells by endocytosis.
    Journal of medicinal chemistry, 2013
    Co-Authors: Markus Nahrwold, Christine Weiß, Tobias Bogner, Felix Mertink, Jens Conradi, Benedikt Sammet, Ralf Palmisano, Soledad Royo Gracia, Thomas Preuße, Norbert Sewald
    Abstract:

    Tumor targeting anticancer drug conjugates that contain a tumor recognition motif (homing device) are of high current relevance. Cryptophycins, naturally occurring cytotoxic cyclo-depsipeptides, have been modified by total synthesis to provide analogues suitable for conjugation to peptide-based homing devices. An array of functionalized β(2)-amino acids was synthesized and incorporated into Cryptophycins. All analogues proved to be highly active in the cytotoxicity assay using the human cervix carcinoma cell line KB-3-1 and its multidrug-resistant subclone KB-V1. Conformational analysis of Cryptophycin-52 and two synthetic analogues was performed by NMR and MD methods to obtain information on the influence of the unit C configuration on the overall conformation. An azide-functionalized Cryptophycin was connected by CuAAC to an alkyne-containing fluorescently labeled cyclic RGD-peptide as the homing device for internalization studies. Confocal fluorescence microscopy proved integrin-mediated internalization by endocytosis and final lysosomal localization of the Cryptophycin prodrug.

  • Approaches for the synthesis of functionalized Cryptophycins.
    The Journal of organic chemistry, 2010
    Co-Authors: Benedikt Sammet, Christine Weiß, Markus Nahrwold, Tobias Bogner, Norbert Sewald
    Abstract:

    The first syntheses of bioactive Cryptophycins functionalized at unit D were accomplished in a one-pot Staudinger reduction/cyclization step. An azido precursor for the lower part of the backbone was introduced to minimize protective group chemistry and enable a very convenient synthesis of Cryptophycin-52 and unit D Cryptophycin analogues containing an ester or a free carboxylic acid for bioconjugations. Both new Cryptophycin derivatives show high biological activity in cytotoxicity assays.

  • "Clicktophycin-52": a bioactive Cryptophycin-52 triazole analogue.
    Organic letters, 2010
    Co-Authors: Markus Nahrwold, Tobias Bogner, Stefan Eissler, Spart Verma, Norbert Sewald
    Abstract:

    An endocyclic trans-amide linkage within the macrocyclic antitumor agent Cryptophycin-52 was replaced by a 1,4-disubstituted 1H-1,2,3-triazole ring. Macrocyclisation of the triazole analogue was accomplished by macrolactamization as well as by Cu(I)-mediated “click”-cyclization. Compared to Cryptophycin-52, in vitro cytotoxicity of “clicktophycin-52” against the multidrug resistant human cancer cell line KB-V1 is only slightly reduced.

  • Efficient Synthesis of Cryptophycin‐52 and Novel para‐Alkoxymethyl Unit A Analogues
    Chemistry (Weinheim an der Bergstrasse Germany), 2009
    Co-Authors: Stefan Eissler, Tobias Bogner, Markus Nahrwold, Norbert Sewald
    Abstract:

    Cryptophycins are a family of highly cytotoxic, cyclic depsipeptides. They display antitumour activity that is largely maintained for multidrug-resistant tumour cells. Cryptophycins are composed of four building blocks (units A-D) that correspond to the respective amino and hydroxy acids. A new synthetic route to unit A allows the selective generation of all four stereogenic centres in a short, efficient and reliable synthesis and contributes to an easier and faster synthesis of Cryptophycins. The first two stereogenic centres are introduced by a catalytic asymmetric dihydroxylation, whereas the remaining two stereogenic centres are introduced with substrate control of diastereoselectivity. The stereogenic diol function also serves as the epoxide precursor. The approach was used to synthesise the native unit A building block as well as three para-alkoxymethyl analogues from which Cryptophycin-52 and three analogous Cryptophycins were prepared. Macro-cyclisation of the seco-depsipeptides was based on ring-closing metathesis.

David H. Sherman - One of the best experts on this subject based on the ideXlab platform.

  • A Versatile Chemoenzymatic Synthesis for the Discovery of Potent Cryptophycin Analogs.
    ACS chemical biology, 2020
    Co-Authors: Jennifer J. Schmidt, Yogan Khatri, Scott I Brody, Catherine Zhu, Halina Pietraszkiewicz, Frederick A. Valeriote, David H. Sherman
    Abstract:

    The Cryptophycins are a family of macrocyclic depsipeptide natural products that display exceptionally potent antiproliferative activity against drug-resistant cancers. Unique challenges facing the synthesis and derivatization of this complex group of molecules motivated us to investigate a chemoenzymatic synthesis designed to access new analogs for biological evaluation. The Cryptophycin thioesterase (CrpTE) and the Cryptophycin epoxidase (CrpE) are a versatile set of enzymes that catalyze macrocyclization and epoxidation of over 20 natural Cryptophycin metabolites. Thus, we envisioned a drug development strategy involving their use as standalone biocatalysts for production of unnatural derivatives. Herein, we developed a scalable synthesis of 12 new unit A-B-C-D linear chain elongation intermediates containing heterocyclic aromatic groups as alternatives to the native unit A benzyl group. N-Acetyl cysteamine activated forms of each intermediate were assessed for conversion to macrocyclic products using wild type CrpTE, which demonstrated the exceptional flexibility of this enzyme. Semipreparative scale reactions were conducted for isolation and structural characterization of new Cryptophycins. Each was then evaluated as a substrate for CrpE P450 and its ability to generate the epoxidized products from these substrates that possess altered electronics at the unit A styrenyl double bond position. Finally, biological evaluation of the new Cryptophycins revealed a des-β-epoxy analog with low picomolar potency, previously limited to Cryptophycins bearing epoxide functionality.

  • Analysis of the Cryptophycin P450 epoxidase reveals substrate tolerance and cooperativity.
    Journal of the American Chemical Society, 2008
    Co-Authors: Yousong Ding, Wolfgang Seufert, Zachary Q. Beck, David H. Sherman
    Abstract:

    Cryptophycins are potent anticancer agents isolated from Nostoc sp. ATCC 53789 and Nostoc sp. GSV 224. The most potent natural Cryptophycin analogues retain a β-epoxide at the C2′−C3′ position of the molecule. A P450 epoxidase encoded by crpE recently identified from the Cryptophycin gene cluster was shown to install this key functional group into Cryptophycin-4 (Cr-4) to produce Cryptophycin-2 (Cr-2) in a regio- and stereospecific manner. Here we report a detailed characterization of the CrpE epoxidase using an engineered maltose binding protein (MBP)−CrpE fusion. The substrate tolerance of the CrpE polypeptide was investigated with a series of structurally related Cryptophycin analogues generated by chemoenzymatic synthesis. The enzyme specifically installed a β-epoxide between C2′ and C3′ of cyclic Cryptophycin analogues. The k cat/Km values of the enzyme were determined to provide further insights into the P450 epoxidase catalytic efficiency affected by substrate structural variation. Finally, binding...

  • Enzymatic Release and Macrolactonization of Cryptophycins from a Safety‐Catch Solid Support
    Angewandte Chemie (International ed. in English), 2007
    Co-Authors: Wolfgang Seufert, Zachary Q. Beck, David H. Sherman
    Abstract:

    the enzymes by a thioester, and in the final step cyclized by an integrated C-terminal thioesterase (TE) domain. The analogy of NRP and PKbiosynthesis to solid-phase synthetic methodology inspired us to develop a solid-phase chemoenzymatic synthetic approach for Cryptophycins and potential analogues. Previous successful strategies for the synthesis and enzyme-catalyzed on-resin cyclization of peptides involved substrates bound by means of an ester or thioester linkage to a solid support. [2] In addition, recent reports of solid-phase synthesis of linear polyketides under diverse reaction conditions encouraged us to design a chemoenzymatic on-resin macrocyclization strategy using a robust linker that is stable to most chemical synthesis conditions. [3] To facilitate the synthesis of large libraries of macrocyclic compounds we also required a method suitable for the direct release and cyclization of compounds on-resin. This model study describes the solid-phase synthesis and on-resin cyclization of three Cryptophycin analogues. Cryptophycins, a class of macrocyclic depsipeptides, were first isolated in the 1990s from Nostoc sp. ATCC 53789 and Nostoc sp. GSV 224. [4] The therapeutic potential of these

  • Biosynthetic characterization and chemoenzymatic assembly of the Cryptophycins. Potent anticancer agents from cyanobionts.
    ACS chemical biology, 2006
    Co-Authors: Nathan A. Magarvey, Richard E. Moore, Trimurtulu Golakoti, Yousong Ding, Zachary Q. Beck, Udo Huber, Thomas K. Hemscheidt, Dafna Abelson, David H. Sherman
    Abstract:

    The lichen cyanobacterial symbiont Nostoc sp. ATCC 53789 and its close relative Nostoc sp. GSV 224 are prolific producers of natural products, generating >25 derivatives of the Cryptophycin class of secondary metabolites. Cryptophycin 1, the prototypic member of the class, is a potent tubulin-depolymerizing agent, and several semisynthetic derivatives are being developed as anticancer therapeutics. Here we provide a detailed characterization of the Cryptophycin metabolic pathway by stable-isotope labeling experiments and through cloning, sequencing, and annotating the Cryptophycin biosynthetic gene cluster. A comparative secondary metabolomic analysis based on polyketide (PK)/non-ribosomal peptide gene clusters from the phylogenetically related, non-Cryptophycin producing cycad symbiont, Nostoc punctiforme ATCC 29133, was used to identify the Cryptophycin biosynthetic genes that encompass approximately 40 kb within the lichen symbiont Nostoc sp. ATCC 53789 genome. The pathway encodes a collinear set of enzymes, including three modular PK synthases, two non-ribosomal peptide synthetase modules, and an integrated adenylation/ketoreductase didomain for elaboration of the leucic acid subunit. In addition, genes encoding key tailoring steps, including a FAD-dependent halogenase and CYP450 epoxidase, were identified. The inherent flexibility of the Cryptophycin biosynthetic enzymes was harnessed to generate a suite of new analogues by altering the pool of PK starter units and selected amino acid extender groups. Characterization of the Cryptophycin CYP450 enabled development of the first stereospecific synthesis of Cryptophycin 2, through a tandem chemoenzymatic synthesis from the natural seco-Cryptophycin 4 chain elongation intermediate.

  • Chemoenzymatic synthesis of Cryptophycin/arenastatin natural products.
    Biochemistry, 2005
    Co-Authors: Zachary Q. Beck, Gunda I. Georg, Nathan A. Magarvey, Courtney C. Aldrich, David H. Sherman
    Abstract:

    Microbially derived modular polyketide synthase and nonribosomal peptide synthetase biosynthetic pathways are a rich source of novel natural products. Development of these systems for the engineered biosynthesis of diverse secondary metabolites continues to progress as a robust source of chemical diversity. Recent efforts that employ individual enzymes and catalytic domains for the production or modification of small molecules have met with growing success. In this study, the thioesterase domain from the Cryptophycin biosynthetic pathway was isolated and its function evaluated with a series of linear chain elongation intermediates in developing a novel chemoenzymatic synthesis of the Cryptophycin/arenastatin class of antitumor agents. The results show the high efficiency of the thioesterase in generating the 16-membered depsipeptide ring of this important natural product system. Moreover, analysis of selected substrates revealed considerable tolerance for structural variation within the seco-Cryptophycin ...