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M. Mahmun Hossain - One of the best experts on this subject based on the ideXlab platform.
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Dynamic kinetic resolution of racemic Tropic Acid ethyl ester and its derivatives
2007Co-Authors: Mary Rose Atuu, M. Mahmun HossainAbstract:Abstract The dynamic kinetic resolution of racemic mixtures of Tropic Acid ethyl ester under substrate racemizing conditions was studied using lipase PS with a ruthenium catalyst. Isopropenyl acetate was used as an acyl donor, since it was found to be compatible with both catalysts; this resulted in an efficient dynamic kinetic resolution. With this process, a variety of racemic Tropic Acid ethyl esters were transformed to optically active acetoxy-2-arylpropionic Acid ethyl esters with 60–88% yields and 53–92% ee.
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Kinetic resolution of Tropic Acid ethyl ester and its derivatives by lipase PS
2004Co-Authors: Mary Rose Atuu, Syed J. Mahmood, Frank Laib, M. Mahmun HossainAbstract:Abstract The first kinetic resolution of Tropic Acid ethyl ester (TAEE) with lipase PS and vinyl acetate as an acylating agent is reported. The resulting (S)-(−)-3-acetoxy Tropic Acid ethyl ester and (R)-(+)-Tropic Acid ethyl ester are produced in high yields and in excellent ee (87–94%). The method has been extended to resolve a variety of Tropic Acid ester derivatives. In addition, an improved method for the preparation of racemic mixtures of Tropic Acid ethyl ester and its derivatives from 3-hydroxy-2-phenylacrylic Acid ethyl ester using NaBH4 in methanol is reported. This procedure is better than the previous ones because it is cleaner, safer and can be worked up easily. An improved method of deacylating the chiral 3-acetoxy Tropic Acid ethyl ester without any loss of stereochemical integrity using HCl/CH3OH is also reported.
Richard J. Robins - One of the best experts on this subject based on the ideXlab platform.
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Tropic Acid ester biosynthesis in datura stramonium and related species
1998Co-Authors: David Ohagan, Richard J. RobinsAbstract:The origin of the Tropic Acid ester moiety, found in some of the tropane alkaloids, but particularly in hyoscyamine and scopolamine, has been a subject of discussion and investigation in biosynthesis for many years. Recently it has been shown in Datura stramonium root cultures that hyoscyamine arises by isomerisation of the tropane alkaloid littorine. The mechanism of this isomerisation process is not obvious and in this review we present our recent results and current thinking on this process.
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Tropic Acid biosynthesis the incorporation of rs phenyl 2 18o 2 2h lactate into littorine and hyoscyamine in datura stramonium
1998Co-Authors: Chi W Wong, David Ohagan, John T G Hamilton, Richard J. RobinsAbstract:The incorporation of oxygen-18 from (RS)-phenyl- [2-18O,2-2H]lactate into the tropane alkaloids littorine 1 and hyoscyamine 2 in Datura stramonium reveals that up to 29% of the oxygen-18 is lost during the transformation of 1 to 2.
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The biosynthesis of Tropic Acid: the stereochemical course of the mutase involved in hyoscyamine biosynthesis in Datura stramonium
1995Co-Authors: Nicola C J E Chesters, Richard J. Robins, David O'hagan, Allen Kastelle, Heinz G. FlossAbstract:Incubation of (R,S)-DL-phenyl[2-3H]lactic Acid with Datura stramonium generates hyoscyamine 2 with the tritium isotope located at C-3′ of the Tropic Acid ester moiety; the C-3′ hydroxymethyl group of 2 is converted into a chiral methyl group and is oxidised to generate chiral sodium acetate, with the (R) configuration (96% ee); the tritium is therefore located at the 3′-pro-S site of 2; it follows that the 3′-pro-R hydrogen is introduced with inversion of configuration by the mutase operating during hyoscyamine biosynthesis.
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the biosynthesis of Tropic Acid the r d phenyllactyl moiety is processed by the mutase involved in hyoscyamine biosynthesis in datura stramonium
1995Co-Authors: Nicola C J E Chesters, David Ohagan, Richard J. RobinsAbstract:Incubations of (R)-D-phenyl[2-13C, 2H]lactic Acid 5a and (S)-L-phenyl[2-13C, 2H]lactic Acid 5b with transformed root cultures of Datura stramonium have revealed that the 13C–2H bond is retained, intact at C-3 of the tropate moiety of hyoscyamine, only in the case of the (R)-D enantiomer 5a( the deuterium is lost from the (S)-L-enantiomer 5b); therefore, it is the (R)-D-phenyllactate moiety of littorine which is the enantiomer processed by the mutase in hyoscyamine biosynthesis.
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Phenyllactic Acid but not Tropic Acid is an intermediate in the biosynthesis of tropane alkaloids in Datura and Brugmansia transformed root cultures
1994Co-Authors: Richard J. Robins, Morteza Ansarin, Jack G Woolley, John Eagles, Brian J. GoodfellowAbstract:(S)-(-)-Tropic Acid is the Acidic moiety of the tropane ester alkaloids, hyoscyamine and scopolamine (hyoscine). When Tropic Acid is fed to transformed root cultures of Datura stramonium L. or a Brugmansia (Datura) Candida x B. aurea hybrid, the formation of these alkaloids is inhibited. Phenyllactic Acid, from which the tropoyl moiety is derived, is considerably less inhibitory. Label from (RS)-phenyl[1,3-13C2]lactic Acid is incorporated at high levels into apoatropine, littorine, aposcopolamine, hyoscyamine, 7β-hydroxyapoatropine, scopolamine and 7β-hydroxyhyoscyamine when fed to these cultures. The presence of an excess concentration of unlabelled Tropic Acid has little influence on the specific incorporation into these products. It is concluded that free Tropic Acid is not an intermediate in hyoscyamine biosynthesis but rather that the rearrangement of phenyllactic Acid occurs subsequent to its esterification.
Mary Rose Atuu - One of the best experts on this subject based on the ideXlab platform.
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Dynamic kinetic resolution of racemic Tropic Acid ethyl ester and its derivatives
2007Co-Authors: Mary Rose Atuu, M. Mahmun HossainAbstract:Abstract The dynamic kinetic resolution of racemic mixtures of Tropic Acid ethyl ester under substrate racemizing conditions was studied using lipase PS with a ruthenium catalyst. Isopropenyl acetate was used as an acyl donor, since it was found to be compatible with both catalysts; this resulted in an efficient dynamic kinetic resolution. With this process, a variety of racemic Tropic Acid ethyl esters were transformed to optically active acetoxy-2-arylpropionic Acid ethyl esters with 60–88% yields and 53–92% ee.
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Kinetic resolution of Tropic Acid ethyl ester and its derivatives by lipase PS
2004Co-Authors: Mary Rose Atuu, Syed J. Mahmood, Frank Laib, M. Mahmun HossainAbstract:Abstract The first kinetic resolution of Tropic Acid ethyl ester (TAEE) with lipase PS and vinyl acetate as an acylating agent is reported. The resulting (S)-(−)-3-acetoxy Tropic Acid ethyl ester and (R)-(+)-Tropic Acid ethyl ester are produced in high yields and in excellent ee (87–94%). The method has been extended to resolve a variety of Tropic Acid ester derivatives. In addition, an improved method for the preparation of racemic mixtures of Tropic Acid ethyl ester and its derivatives from 3-hydroxy-2-phenylacrylic Acid ethyl ester using NaBH4 in methanol is reported. This procedure is better than the previous ones because it is cleaner, safer and can be worked up easily. An improved method of deacylating the chiral 3-acetoxy Tropic Acid ethyl ester without any loss of stereochemical integrity using HCl/CH3OH is also reported.
Jack G Woolley - One of the best experts on this subject based on the ideXlab platform.
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the biosynthesis of Tropic Acid part 6 enantioselective intact incorporation of r 3 phenyllactic Acid into the Tropic Acid ester alkaloids of datura
1995Co-Authors: Morteza Ansarin, Jack G WoolleyAbstract:(R)-(+)-11 and (S)-(–)3-Phenyl[1,3-13C2; 1-14C] lactic Acid 13 were fed separately to Datura stramonium(Solanaceae)via the wick method. In a second feeding experiment (R)-(+)- and (S)-(–)-3-phenyl [1,3-13C2; 2-14C] lactic Acid were administered via the roots. In both cases hyoscine (scopolamine) and hyoscyamine 1 and 2, respectively were isolated separately from the roots and aerial parts. The (R)-enantiomer 11 was more efficiently incorporated into the (S)-(–)-Tropic Acid 8 moiety of both bases. Examination of the 13C NMR spectra of the bases and of Tropic Acid, obtained by hydrolysis of hyoscyamine, showed 13C–13C spin–spin coupling indicating that the tropoyl ester (–)-hyoscyamine 9 is formed by direct rearrangement of the (R)-(+)-3-phenyllactic Acid 11 ester of tropine (littorine).
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the rearrangement of phenyllactate in the biosynthesis of Tropic Acid
1994Co-Authors: Morteza Ansarin, Jack G WoolleyAbstract:Abstract Phenyl[1,3-13C2]lactic Acid was synthesized and fed to Datura stramonium via the wick method and via the roots. Hyoscine (scopolamine) and hyoscyamine were isolated, and examination of their 13C NMR spectra showed spin-spin coupling from the newly formed contiguous centres, indicating that Tropic Acid is formed by an intramolecular rearrangement of phenyllactate.
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Phenyllactic Acid but not Tropic Acid is an intermediate in the biosynthesis of tropane alkaloids in Datura and Brugmansia transformed root cultures
1994Co-Authors: Richard J. Robins, Morteza Ansarin, Jack G Woolley, John Eagles, Brian J. GoodfellowAbstract:(S)-(-)-Tropic Acid is the Acidic moiety of the tropane ester alkaloids, hyoscyamine and scopolamine (hyoscine). When Tropic Acid is fed to transformed root cultures of Datura stramonium L. or a Brugmansia (Datura) Candida x B. aurea hybrid, the formation of these alkaloids is inhibited. Phenyllactic Acid, from which the tropoyl moiety is derived, is considerably less inhibitory. Label from (RS)-phenyl[1,3-13C2]lactic Acid is incorporated at high levels into apoatropine, littorine, aposcopolamine, hyoscyamine, 7β-hydroxyapoatropine, scopolamine and 7β-hydroxyhyoscyamine when fed to these cultures. The presence of an excess concentration of unlabelled Tropic Acid has little influence on the specific incorporation into these products. It is concluded that free Tropic Acid is not an intermediate in hyoscyamine biosynthesis but rather that the rearrangement of phenyllactic Acid occurs subsequent to its esterification.
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competitive feeding experiments with Tropic Acid precursors in datura
1993Co-Authors: Morteza Ansarin, Jack G WoolleyAbstract:Phenyl{1- 14 C}alanine {3}, phenyl{2- 14 C}pyruvate {4}, and phenyl{1- 14 C}lactate {5} were fed singly and in competition with unlabeled phenylalanine, phenyllactate, and phenylpyruvate to Datura stramonium. The activities recorded in the alkaloids hyoscyamine {1} and hyoscine (scopolamine) {2} suggested that phenyllactate {5} was the closest precursor for the Tropic Acid moiety of these alkaloids. Hyoscyamine {1}, from plants fed with phenyl{2- 14 C}pyruvate {5}, was hydrolyzed, but the resultant Tropic Acid 7 contained only 21% of the activity, the remainder being located in the tropine
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the obligatory role of phenyllactate in the biosynthesis of Tropic Acid
1993Co-Authors: Morteza Ansarin, Jack G WoolleyAbstract:Abstract Phenyl[1-14C] lactic Acid and phenyl [2-3H] lactic Acid were synthesized by conventional routes and fed in admixture (3H:14C ratio 10:1) to Datura stramonium via the roots. Hyoscine (scopolamine) and hyoscyamine were isolated and found to have essentially the same 3H:14C ratios as the precursor (8.5 and 10.15, respectively). Hydrolysis of hyoscyamine showed that all the activity was present in the Tropic Acid moiety. The Tropic Acid was converted to aTropic Acid and then cleaved by means of osmium tetroxide and sodium metaperiodate to yield formaldehyde containing all the tritium and phenylglyoxylic Acid containing all the 14C, a result which shows that the tritium at C-2 of the phenyllactate precursor labelled Tropic Acid in the hydroxymethyl group. These findings show that phenyllactate is an obligatory intermediate in the biosynthesis of Tropic Acid and that the rearrangement of the side-chain takes place at the phenyllactate and not the phenylpyruvate level.
J B Robinson - One of the best experts on this subject based on the ideXlab platform.
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preparation and characterization of the Tropic Acid esters of tropan 3β ol granatan 3α ol and granatan 3β ol
2011Co-Authors: R J Hunt, J B RobinsonAbstract:The preparation and characterization of the Tropic Acid esters of tropan-3β-ol and granatan-3α and 3β-ol are reported. A rapid synthesis of pseudopelletierine is described.