Carolacton, a secondary metabolite, was isolated from the myxobacterium Sorangium cellulosum. It exhibits excellent antibacterial activity at nanomolar concentrations. We report the synthesis of the macrocyclic core of carolacton, comprising the C7-C19 fragment with five out of the eight stereocentres. The key reactions involved are: Sharpless asymmetric epoxidation, metal chelated epoxide opening, Yamaguchi esterification and ring closing metathesis (RCM). The present study utilizes a simple synthetic strategy, adopting asymmetric and chiron approaches.

Cyclic b 2,3 -amino acids though have been extensively used in foldamer designs, their acyclic analogues have received less attention. In view of strong backbone constraints imparted by the substituents, b 2,3 -amino acids provide very attractive options for creating novel foldamers. In the present study, new C-linked carbo-b 2,3 -amino acids (b 2,3 -Caa) were prepared by the alkylation of Ca-carbon (C2) with allyl and propargyl halides, and used with L-Ala to design regular 1 : 1 hybrid a/b 2,3 -peptides. Extensive NMR and MD studies revealed the presence of right-handed 11/9-mixed helices in the peptides with the 'a-b-a' sequence at the C-terminus, while, induction of 'turns' in the peptides with the 'b-a-b' motif at the C-terminus. Despite the strong backbone constraints due to the substitution at both the b 2 and b 3 -carbons, the folds of these a/b 2,3 -peptides are less robust compared to foldamers of the a/b 3 -family, reflecting the impact of Ca-substitution.

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A simple and efficient protocol was developed for the synthesis of aryl azides directly from aryl carbinols using ZrCl 4 as a Lewis acid catalyst. The azides were converted to novel triazoles under click reaction conditions and evaluated the resulting triazoles for their antimicrobial activity against various strains.