Enantio- and diastereo-convergent synthesis of (2R,5R)- and (2R,5S)-Pityol through enzyme-triggered ring closure
摘要:
A short chemoenzymatic synthesis of the (2R,5S)- and (2R,5R)-stereoisomer of the bark beetle pheromone Pityol 1 was achieved from (+/-)-Sulcatol 2 in an enantio- and diastereo-convergent fashion without the formation of any 'unwanted' stereoisomer. The key steps include: (i) lipase-catalyzed deracemization of (+/-)-2 using kinetic resolution coupled to an in-situ inversion or alternatively, dynamic resolution using combined lipase- and Ru-catalysis: and (ii) creation of the second stereogenic center by an epoxide hydrolase-catalyzed diastereo-convergent hydrolysis of a haloalkyl oxirane, followed by spontaneous ring Closure to form 1 in a stereoselective fashion. (C) 2001 Published by Elsevier Science Ltd.
Diastereoselective Titanocene-Catalyzed Oxidative Cyclization of Bishomoallylic Alcohols
作者:Alessandra Lattanzi、Giorgio Della Sala、Maurizio Russo、Arrigo Scettri
DOI:10.1055/s-2001-16779
日期:——
Bishomoallylic alcohols are converted in good yields and diastereoselectivity into tetrahydrofuranols and tetrahydropyranols by Cp2TiCl2/t-butyl hydroperoxide/activated 4 Å molecular sieves system.
A new synthetic process for the construction of oxygen-containing heterocyclic systems starting from bicyclic acetals is described. We have investigated the mechanism and the stereochemicalcourse of the reductive cleavage of acetals.
Stereocontrolled oxidation of 5-hydroxyalkenes with rhenium oxide. III
作者:Suhan Tang、Robert M. Kennedy
DOI:10.1016/s0040-4039(00)79077-0
日期:1992.9
5-Hydroxyalkenes react with rhenium (VII) oxide (Re2O7) to provide 2-hydroxymethyl-tetrahydrofurans. Oxidation occurs with overall syn addition to the alkene. Stereoselectivity is easily understood by invoking [2+2] cycloaddition followed by reductive elimination.
5-羟基烯烃与氧化((Re 2 O 7)反应,生成2-羟甲基-四氢呋喃。氧化与烯烃的全部合成物加成一起发生。通过调用[2 + 2]环加成,然后进行还原性消除,可以轻松理解立体选择性。
Stereoselective reduction of bicyclic acetals. A method for reductive generation of heterocyclic ring systems
Directed oxidative cyclization of 5-hydroxyalkenes with rhenium oxide
作者:Robert M. Kennedy、Suhan Tang
DOI:10.1016/0040-4039(92)80010-h
日期:1992.6
5-Hydroxyalkenes react with rhenium(VII) oxide (Re2O7) to provide 2-hydroxymethyltetrahydrofurans. Oxidative cyclization occurs with overall syn addition to the alkenes in moderate yields with little tendency toward oxidation of alcohols to carbonyl compounds.