Regioselective and stereoselective reductive cleavage of 1,7-dioxaspiro[5.5]undecane alcohols
摘要:
Lewis acid-promoted triethylsilane reduction of 6,6-spiroketol alcohols produces cis-2,6-disubstituted tetrahydropyrans with excellent regioselectivity and stereocontrol. An appended alcohol allows bidentate coordination of the Lewis acid to selectively activate one CO bond of the anomeric center toward reductive cleavage. Copyright (C) 1996 Elsevier Science Ltd
Studies directed toward the total synthesis of pinnatoxin A: synthesis of the 6,5,6-dispiroketal (BCD ring) system by double hemiketal formation/hetero-Michael addition strategy
An efficient, highly stereoselective synthesis of the C10–C26 portion of pinnatoxin A has been achieved, wherein the key step is a highly stereoselective construction of the 6,5,6-dispiroketal (BCD ring) system by an intramolecular hetero-Michael addition of a hemiketal alkoxide reversibly formed under the influence of lithium methoxide.
[reaction: see text] An efficient synthesis of the C10-C31 (BCDEF ring) portion of pinnatoxin A has been achieved. The key step is a highly stereoselective construction of the dispiroketal (BCD ring) system employing an intramolecular hetero-Michael reaction of a reversibly formed hemiketal alkoxide through the use of LiOMe.
(R, Z)-7,15-Hexadecadien-4-olide, the sexpheromone of the yellowishelongatechafer (Heptophyllapicea), was synthesized from l-malic acid in 15 steps. The synthetic pheromone was identical with the natural product in its MS, IR, GLC retention time, and biological activity.
Optically active compound having a .delta.-valerolactone ring and liquid
申请人:Mitsubishi Rayon Company Ltd.
公开号:US05480580A1
公开(公告)日:1996-01-02
Optical active compounds which are chemically stable, are not colored, have a good optical stability, and which give a liquid crystal composition having a large spontaneous polarization when the compound is incorporated, are provided. The optical active compound have an asymmetric carbon atom fixed by a .delta.-valerolactone ring and the permanent dipole moment derived from the carboxylic group is fixed by the .delta.-valerolactone ring and two alkyl groups which can be regarded as a part of a measogen.