Asymmetric Catalysis Route to anti,anti Stereotriads, Illustrated by Applications
摘要:
A short sequence based on asymmetric catalysis, chirality transfer, and an optimized carbometallation protocol gave an anti,anti stereotriad building block in six steps. Both enantiomers of the chirality source, N-methyl ephedrine, are inexpensive, and the auxiliary is recoverable. In one chiral series, the building block was converted to the "B-2" intermediate in Miyashita's synthesis of scytophycin C; in the enantiomeric series, it was converted to a key intermediate for aplyronine A and to the polyketide "cap" for the callipeltins.
Stereoselective synthesis of (2R,3R,4R)-3-hydroxy-2,4,6-trimethylheptanoic acid and determination of the absolute stereochemistry of the natural product from callipeltin A
摘要:
A revised stereostructure of 3-hydroxy-2,4,6-trimethylheptanoic acid, the beta-hydroxy acid that acylates the N-terminus of callipeltin A. is proposed on the basis of analysis of J-coupling in the H-1 NMR spectrum of the acetonide derivative obtained front the acid hydrolysate of callipeltin A. The proposed Structure was definitively confirmed by enantioselective synthesis. (C) 2002 Elsevier Science Ltd. All rights reserved.