Stereoselective synthesis of β-amino-γ-butyrolactones
摘要:
A novel synthesis of optically active beta-amino-gamma-butyrolactones is described. O-Silylated (R)-cyanohydrins (R)-3 (derived from aldehydes 1 by (R)-hydroxynitrile lyase ((R)-PaHNL)-catalyzed addition of HCN) were reacted with allyl Grignard to give amino alcohols (4R,5S)-5 after reduction. In the addition of crotyl Grignard reagent, workup conditions are decisive for the formation of amino alcohol 8, which was isolated Lis a diastercoisomeric mixture the acetylated main diastereoisomer (3S,4R,5R)-10 was separated. Ozonolysis of the acetylated amino alcohols (4S,5R)-7a,b and (3S,4S,5R)-10 affords the aldehydes 12a-c, which were directly oxidized with CrO3 in dilute H2SO4 to yield the beta-acetamido-gamma-acetoxycarboxylic acids (3S,4R)-13a,b and (2R,3S,4R)-13c. Compounds 13 cyclized spontaneously Under acidic conditions to afford beta-acetamido-gamma-butyrolactones (4S,5R)-14a,b and (3R,4S,5R)-14c. (C) 2002 Elsevier Science Ltd. All rights reserved.
Asymmetric addition of trimethylsilyl cyanide to aldehydes promoted by chiral polymeric vanadium(V) salen complex as an efficient and recyclable catalyst
作者:Noor-ul H. Khan、Santosh Agrawal、Rukhsana I. Kureshy、Sayed H.R. Abdi、Vishal J. Mayani、Raksh V. Jasra
DOI:10.1016/j.tetasy.2006.09.024
日期:2006.10
The asymmetric addition of trimethylsilyl cyanide to various aldehydes catalyzed by efficient new vanadyl polymeric salen complexes having 12 repeating salen units was investigated at room temperature. An excellent yield of the trimethylsilylether of cyanohydrins (up to 98%) with high chiral induction (96%) in case of 2-methylbenzaldehyde was achieved in 18 h. The catalyst recovered four times with