A New Tactic for Tocopherol Synthesis Using Intramolecular Benzyne Trapping by an Alcohol
摘要:
A formal total synthesis of (S)-alpha-tocopherol, the major component of natural Vitamin E has been achieved using intramolecular benzyne trapping as a key step to form the chroman ring. The synthesis also features an efficient new method for benzotriazole N-amination using an oxaziridine; chiral, nonracemic intermediates are generated using asymmetric dihydroxylation.This paper is dedicated to Professor Lutz Tietze on his 75th birthday, with all best wishes.
Total Synthesis of Brevetoxin B. 2. Second Generation Strategies and Construction of the Dioxepane Region [DEFG]
作者:K. C. Nicolaou、E. A. Theodorakis、F. P. J. T. Rutjes、M. Sato、J. Tiebes、X.-Y. Xiao、C.-K. Hwang、M. E. Duggan、Z. Yang
DOI:10.1021/ja00146a009
日期:1995.10
examined with a variety of aldehydes (e.g., 39, 59, and 62). Construction of 38 was thus achieved from vinyl triflate 36 and the ring B aldehyde 39. However, the projected intramolecular Michael addition (41 — ■ 1 42) and reductive hydroxy ketone cyclization (47 48) failed to yield ring C. Fetizon cyclization afforded the pentacyclic lactone (CDEFG) (51 — * 52), which resisted further useful functionalization
Enantioselective Total Syntheses of (<i>R</i>)- and (<i>S</i>)-Naphthotectone, and Stereochemical Assignment of the Natural Product
作者:Guillermo A. Guerrero-Vásquez、Flávia A. D. Galarza、José M. G. Molinillo、Carlos Kleber Z. Andrade、Francisco A. Macías
DOI:10.1002/ejoc.201501479
日期:2016.3
core of the final products was obtained by a late-stage anodic treatment. (R)-Naphthotectone was obtained in six steps from leuconaphthazarin with an overall yield of 38 % and an enantiomeric excess of 86 %. This compound was found to have the same absolute configuration as the natural product at its C-3′ stereogenic center. (S)-Naphthotectone was obtained in five steps from leuconaphthazarin with an
Stereochemische Korrelationen zwischen (2<i>R</i>,4′<i>R</i>,8′<i>R</i>)-α-Tocopherol, (25<i>S</i>,26)-Dihydroxycholecalciferol, (-)-(1<i>S</i>,5<i>R</i>)-Frontalin und (-)-(<i>R</i>)-Linalol
作者:Richard Barner、Josef Hübscher
DOI:10.1002/hlca.19830660321
日期:1983.5.5
StereochemicalCorrelations between (2R,4′R,8′R)-α-Tocopherol, (25S,26)-Dihydroxycholecalciferol, (–)-(1S,5R)-Frontalin and (–)-(R)-Linalol
Chemo-Enzymatic Enantioconvergent Synthesis of C<sub>4</sub>-Building Blocks Containing a Fully Substituted Chiral Carbon Center using Bacterial Epoxide Hydrolases
作者:Andreas Steinreiber、Helena Hellström、Sandra F. Mayer、Romano V. A. Orru、Kurt Faber
DOI:10.1055/s-2001-9703
日期:——
A highly efficient chemo-enzymatic asymmetric synthesis of chiral C4-building blocks containing a fully substituted carbon center is reported. The key transformation consists of a deracemization based on an enantioconvergent asymmetric hydrolysis of an epoxide using combined bio- and chemo-catalysis leading to a single enantiomeric product in >98% e. e. A simple switch of steps leads to kinetic resolution giving access to products of opposite configuration.
The Role of Phosphate in a Multistep Enzymatic Reaction: Reactions of the Substrate and Intermediate in Pieces
作者:Svetlana A. Kholodar、C. Leigh Allen、Andrew M. Gulick、Andrew S. Murkin
DOI:10.1021/ja512911f
日期:2015.2.25
nonreacting phosphoryl group to accelerate catalysis. Evidence for the involvement of the phosphodianion in transition state formation has come from reactions of the substrate in pieces, in which reaction of a truncated substrate lacking its phosphorylmethyl group is activated by inorganic phosphite. What has remained unknown until now is how the phosphodianion group influences the reaction energetics