Asymmetric Synthesis of the Northern Half C1−C16 of the Bryostatins
摘要:
[GRAPHICS]Starting from 8-oxabicyclo[3.2.1]oct-6-en-3-one and racemic 2,2-dimethyl-8-oxabicyclo[3.2.1]oct-6-en-3-one the C1-C16 segment of the bryostatins has been synthesized in 30 steps and 9% overall yield (17 steps longest linear sequence), Fragment coupling by dithiane strategy and protecting group manipulations provided an advanced chemodifferentiated northern half segment.
Lipase mediated desymmetrization of meso-2,6-di(acetoxymethyl)-tetrahydropyran-4-one derivatives. An innovative route to enantiopure 2,4,6-trifunctionalized C-glycosides
摘要:
The desymmetrization of several meso-configurated 2,4,6-trifunctionalized tetrahydropyrans was studied. Amongst the derivatives investigated the conformationally more rigid spiro ketal 8b afforded hydroxy-acetate (-)-12 in excellent chemical yield and enantiomeric excess. The absolute configuration of the resulting 2,4,6-trifunctionalized C-glycosides was established by X-ray crystal diffraction. Copyright (C) 1996 Elsevier Science Ltd