The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Glenn C. Micalizio - One of the best experts on this subject based on the ideXlab platform.
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synthesis of the cortistatin pentacyclic core by alkoxide directed metallacycle mediated annulative cross coupling
Organic Letters, 2016Co-Authors: Claudio Aquino, Glenn C. Micalizio, Stephen N GreszlerAbstract:The pentacyclic core skeleton of the cortistatins has been prepared in a stereoselective fashion by strategic use of an alkoxide-directed metallacycle-mediated annulative cross-coupling. This metal-centered tandem reaction delivers a polyunsaturated Hydrindane and establishes the C13 stereodefined quaternary center with high levels of stereocontrol. Subsequent regio- and stereoselective global hydroboration results in the realization of the DE-trans ring fusion and a tertiary alcohol at C8. Establishment of the ABC-tricyclic subunit was then accomplished through phenolic oxidation/trans-acetalization, chemoselective reduction, regioselective cleavage, and intramolecular alkylation at C5.
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Synthesis of the Cortistatin Pentacyclic Core by Alkoxide-Directed Metallacycle-Mediated Annulative Cross-Coupling
2016Co-Authors: Claudio Aquino, Stephen N Greszler, Glenn C. MicalizioAbstract:The pentacyclic core skeleton of the cortistatins has been prepared in a stereoselective fashion by strategic use of an alkoxide-directed metallacycle-mediated annulative cross-coupling. This metal-centered tandem reaction delivers a polyunsaturated Hydrindane and establishes the C13 stereodefined quaternary center with high levels of stereocontrol. Subsequent regio- and stereoselective global hydroboration results in the realization of the DE-trans ring fusion and a tertiary alcohol at C8. Establishment of the ABC-tricyclic subunit was then accomplished through phenolic oxidation/trans-acetalization, chemoselective reduction, regioselective cleavage, and intramolecular alkylation at C5
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Synthesis of Neurotrophic Seco-prezizaane Sesquiterpenes (1R,10S)‑2-Oxo-3,4-dehydroneomajucin, (2S)‑Hydroxy-3,4-dehydroneomajucin, and (−)-Jiadifenin
2016Co-Authors: Xiayun Cheng, Glenn C. MicalizioAbstract:An asymmetric approach to the synthesis of neurotrophic seco-prezizaane sesquiterpenes is described that is based on the strategic application of a hydroxyl-directed metallacycle-mediated [2 + 2 + 2] annulation and an intramolecular radical cyclization cascade. Targets prepared are among the most potent members of the natural product class and include (1R,10S)-2-oxo-3,4-dehydroneomajucin, (2S)-hydroxy-3,4-dehydroneomajucin, and (−)-jiadifenin. In addition to representing the first application of the alkoxide-directed metallacycle-mediated Hydrindane-forming annulation reaction in natural product synthesis and the first total synthesis of (2S)-hydroxy-3,4-dehydroneomajucin, these pursuits have resulted in the elucidation of a complex radical cascade process for installation of the C5 quaternary center common to the natural product class
Jerzy Wicha - One of the best experts on this subject based on the ideXlab platform.
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expedited approach to the vitamin d trans Hydrindane building block from the hajos dione comparative study on various methods for the selective deoxygenation of one of the hydroxy groups in a diol
Journal of Organic Chemistry, 2007Co-Authors: Pawel Chochrek, Jerzy WichaAbstract:1α,25-Dihydroxyvitamin D3 (calcitriol, 1) is a bioregulator important for the treatment of various human metabolic diseases and biomedical research. Herein, we report an efficient diastereoselective approach to the key trans-Hydrindane building block for calcitriol synthesis (2a) starting from the readily accessible optically active tetrahydroindenedione derivative (Hajos dione, 3). It was found that epoxide ring opening in a related hydroxy epoxide (7) with sodium cyanoborohydride−BF3 × Et2O occurs by hydride anion addition at the ring juncture position to produce a vicinal diol with the trans-Hydrindane ring system (6a). Four methods for selective deoxygenation of the sterically less shielded hydroxy group in diol 6a were examined with an approach based on a cyclic sulfate of the diol as the most efficient and operationally convenient method.
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a new approach to a vitamin d ring c d building block from the hajos dione involving epoxide opening at the more substituted carbon atom
Tetrahedron Letters, 2006Co-Authors: Pawel Chochrek, Alicja Kurektyrlik, Karol Michalak, Jerzy WichaAbstract:Abstract A new approach to a trans -Hydrindane building block for 1α,25-dihydroxyvitamin D 3 (calcitriol) synthesis from the Hajos dione has been developed. The α,β-unsaturated carbonyl group in the Hajos dione has been protected and the carbonyl group in the five-membered ring has been used for the side chain attachment. Key steps in the six-membered ring transformation include: reduction of the carbonyl group, stereoselective epoxidation of the double bond in the allylic alcohol, opening of the epoxide at the more substituted carbon atom and regioselective deoxygenation.
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an expedited approach to the vitamin d trans Hydrindane building block from the hajos dione
Organic Letters, 2006Co-Authors: Pawel Chochrek, Jerzy WichaAbstract:Efficient and operationally simple synthesis of the key trans-Hydrindane alcohol building block for the synthesis of calicitriol (1α,25-dihydroxyvitamin D3) has been developed. Epoxy alcohol prepared almost quantitatively from the Hajos dione was reduced at the quaternary carbon by the Hutchins procedure (NaBH3CN−BF3·Et2O). The diol was selectively deoxygenized either using the Barton−McCombie reaction (with Bu3SnH−AIBN) or via the respective iodohydrine (with LiAlH4).
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an expedited approach to the vitamin d trans Hydrindane building block from the hajos dione
Organic Letters, 2006Co-Authors: Pawel Chochrek, Jerzy WichaAbstract:Efficient and operationally simple synthesis of the key trans-Hydrindane alcohol building block for the synthesis of calicitriol (1alpha,25-dihydroxyvitamin D(3)) has been developed. Epoxy alcohol prepared almost quantitatively from the Hajos dione was reduced at the quaternary carbon by the Hutchins procedure (NaBH(3)CN-BF(3).Et(2)O). The diol was selectively deoxygenized either using the Barton-McCombie reaction (with Bu(3)SnH-AIBN) or via the respective iodohydrine (with LiAlH(4)). [reaction: see text]
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diastereoselective approaches to trans Hydrindane derivatives total synthesis of 8 phenylsulfonyl de a b cholestane precursors to 25 hydroxyvitamin d3
European Journal of Organic Chemistry, 2002Co-Authors: Igor Prowotorow, Wiaczeslaw Stepanenko, Jerzy WichaAbstract:The total diastereoselective synthesis of the C,D rings/side chain building block for the synthesis of 1α,25-dihydroxyvitamin D3 is described. Two tandem Mukaiyama−Michael additions involving silylated ketene acetals derived from tert-butyl 6-methylhept-5-enethioate or tert-butyl 6-methylhept-6-enethioate, 2-methylcyclopent-2-en-1-one, and 1-(phenylthio)but-3-en-2-one afforded the corresponding intermediates with the complete carbon framework of the target compound. The further transformation of these key intermediates involved cyclization, oxidation with m-CPBA, and reduction of the vinylic sulfone moiety to afford the trans-Hydrindane ring system. The synthesis comprises five operations and afforded the product in ca. 30% yield. The application of 2-[(phenylthio)methyl]-2-vinyl[1,3]dioxolane and 2-(phenylsulfonylmethyl)-2-vinyl[1,3]dioxolane as Michael acceptors was also examined. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)
Maurice Santelli - One of the best experts on this subject based on the ideXlab platform.
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a short and convenient access to a trans Hydrindane unit from the anti meso acetylmethyldivinylcyclopentane via a radical pathway
Tetrahedron Letters, 2006Co-Authors: Annesophie Chapelon, Cyril Ollivier, Maurice SantelliAbstract:Abstract An efficient route for multigram synthesis of a trans -Hydrindane unit, involving a selective 6-endo-trig α-carbonyl radical cyclization of the α-xanthyl ketone 10 derivating from the anti - meso -acetylmethyldivinylcyclopentane 9 through a xanthate group transfer, is achieved in good yield. Preparation of an advanced intermediate for the Julia–Kocienski coupling, used in the elaboration of the trienic system of vitamin D (or calciferol) analogs, was materialized by conversion of the xanthate moiety to a 2-benzothiazole sulfonyl group.
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desymmetrization of the anti meso acetylmethyldivinylcyclopentane by directed epoxidation and its application to the synthesis of a polyfunctionalized trans Hydrindane unit
Synlett, 2006Co-Authors: Raphael Rodriguez, Cyril Ollivier, Maurice SantelliAbstract:Desymmetrization of the anti-meso-acetylmethyldivinyl cyclopentane was realized through a three-step sequence involving reduction of the ketone moiety, bishomoallylic alcohol-directed epoxidation and Dess-Martin oxidationleading to the epoxy ketone as a single diastereoisomer. The epoxy ketone was efficiently converted to a trans-Hydrindane unit, which constitutes an excellent precursor for the preparation of steroids and their seco-B analogues such as vitamin D 3 and its metabolites.
Claudio Aquino - One of the best experts on this subject based on the ideXlab platform.
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synthesis of the cortistatin pentacyclic core by alkoxide directed metallacycle mediated annulative cross coupling
Organic Letters, 2016Co-Authors: Claudio Aquino, Glenn C. Micalizio, Stephen N GreszlerAbstract:The pentacyclic core skeleton of the cortistatins has been prepared in a stereoselective fashion by strategic use of an alkoxide-directed metallacycle-mediated annulative cross-coupling. This metal-centered tandem reaction delivers a polyunsaturated Hydrindane and establishes the C13 stereodefined quaternary center with high levels of stereocontrol. Subsequent regio- and stereoselective global hydroboration results in the realization of the DE-trans ring fusion and a tertiary alcohol at C8. Establishment of the ABC-tricyclic subunit was then accomplished through phenolic oxidation/trans-acetalization, chemoselective reduction, regioselective cleavage, and intramolecular alkylation at C5.
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Synthesis of the Cortistatin Pentacyclic Core by Alkoxide-Directed Metallacycle-Mediated Annulative Cross-Coupling
2016Co-Authors: Claudio Aquino, Stephen N Greszler, Glenn C. MicalizioAbstract:The pentacyclic core skeleton of the cortistatins has been prepared in a stereoselective fashion by strategic use of an alkoxide-directed metallacycle-mediated annulative cross-coupling. This metal-centered tandem reaction delivers a polyunsaturated Hydrindane and establishes the C13 stereodefined quaternary center with high levels of stereocontrol. Subsequent regio- and stereoselective global hydroboration results in the realization of the DE-trans ring fusion and a tertiary alcohol at C8. Establishment of the ABC-tricyclic subunit was then accomplished through phenolic oxidation/trans-acetalization, chemoselective reduction, regioselective cleavage, and intramolecular alkylation at C5
Pawel Chochrek - One of the best experts on this subject based on the ideXlab platform.
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expedited approach to the vitamin d trans Hydrindane building block from the hajos dione comparative study on various methods for the selective deoxygenation of one of the hydroxy groups in a diol
Journal of Organic Chemistry, 2007Co-Authors: Pawel Chochrek, Jerzy WichaAbstract:1α,25-Dihydroxyvitamin D3 (calcitriol, 1) is a bioregulator important for the treatment of various human metabolic diseases and biomedical research. Herein, we report an efficient diastereoselective approach to the key trans-Hydrindane building block for calcitriol synthesis (2a) starting from the readily accessible optically active tetrahydroindenedione derivative (Hajos dione, 3). It was found that epoxide ring opening in a related hydroxy epoxide (7) with sodium cyanoborohydride−BF3 × Et2O occurs by hydride anion addition at the ring juncture position to produce a vicinal diol with the trans-Hydrindane ring system (6a). Four methods for selective deoxygenation of the sterically less shielded hydroxy group in diol 6a were examined with an approach based on a cyclic sulfate of the diol as the most efficient and operationally convenient method.
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a new approach to a vitamin d ring c d building block from the hajos dione involving epoxide opening at the more substituted carbon atom
Tetrahedron Letters, 2006Co-Authors: Pawel Chochrek, Alicja Kurektyrlik, Karol Michalak, Jerzy WichaAbstract:Abstract A new approach to a trans -Hydrindane building block for 1α,25-dihydroxyvitamin D 3 (calcitriol) synthesis from the Hajos dione has been developed. The α,β-unsaturated carbonyl group in the Hajos dione has been protected and the carbonyl group in the five-membered ring has been used for the side chain attachment. Key steps in the six-membered ring transformation include: reduction of the carbonyl group, stereoselective epoxidation of the double bond in the allylic alcohol, opening of the epoxide at the more substituted carbon atom and regioselective deoxygenation.
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an expedited approach to the vitamin d trans Hydrindane building block from the hajos dione
Organic Letters, 2006Co-Authors: Pawel Chochrek, Jerzy WichaAbstract:Efficient and operationally simple synthesis of the key trans-Hydrindane alcohol building block for the synthesis of calicitriol (1α,25-dihydroxyvitamin D3) has been developed. Epoxy alcohol prepared almost quantitatively from the Hajos dione was reduced at the quaternary carbon by the Hutchins procedure (NaBH3CN−BF3·Et2O). The diol was selectively deoxygenized either using the Barton−McCombie reaction (with Bu3SnH−AIBN) or via the respective iodohydrine (with LiAlH4).
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an expedited approach to the vitamin d trans Hydrindane building block from the hajos dione
Organic Letters, 2006Co-Authors: Pawel Chochrek, Jerzy WichaAbstract:Efficient and operationally simple synthesis of the key trans-Hydrindane alcohol building block for the synthesis of calicitriol (1alpha,25-dihydroxyvitamin D(3)) has been developed. Epoxy alcohol prepared almost quantitatively from the Hajos dione was reduced at the quaternary carbon by the Hutchins procedure (NaBH(3)CN-BF(3).Et(2)O). The diol was selectively deoxygenized either using the Barton-McCombie reaction (with Bu(3)SnH-AIBN) or via the respective iodohydrine (with LiAlH(4)). [reaction: see text]
