One-Pot Rhodium(I)-Catalyzed Hydroboration of Alkenes: Radical Conjugate Addition
作者:Philippe Renaud、Cyril Ollivier、Valéry Weber
DOI:10.1021/jo034515v
日期:2003.7.1
B-Alkylcatecholboranes, prepared by rhodium(I)-catalyzed hydroboration of alkenes, are suitable radical precursors for conjugate addition to activated olefins. This procedure proved to be particularly useful for the control of the regio- and chemoselectivity of such tandem processes. Enantioselective hydroboration has also been successfully coupled with radical chain reaction in a one-pot process.
Chiral norbornane-type alcohols of high optical purity were prepared via enzymaticresolution of their racemic esters using lipases from Candida cylindracea and Pseudomonas sp. This method presents a short and efficient access to a number of chiral building blocks on a molar scale for the synthesis of optically active cyclopentane systems.
Synthesis and conformational studies of peptidomimetics containing a carbocyclic 1,3-diacid
作者:Tushar K Chakraborty、Animesh Ghosh、R Nagaraj、A Ravi Sankar、Ajit C Kunwar
DOI:10.1016/s0040-4020(01)00921-8
日期:2001.10
A rigid carbocyclic scaffold comprising of an all-cis 4,5-dihydroxy-1,3-cyclopentanedicarboxylic acid is developed. Attachment of peptide strands to the carboxylic groups of this novel template led to the peptidomimetics 2 and 3. Conformational analysis by circular dichroism and NMR studies revealed that these molecules adopt a unique folded structure in nonpolar solvent involving intramolecular hydrogen bonding between PheNH of one strand and LeuC=O (in 2) or GlyC=O (in 3) of the other strand. This structure is very different from the structures observed earlier in their sugar counterparts (1). The paper describes in detail the synthesis and structural studies of compounds 2 and 3. (C) 2001 Elsevier Science Ltd. All rights reserved.