Acta Crystallographica Section C

Crystal Structure Communications

Volume 61, Part 2 (February 2005)

organic compounds

fa1106 scheme

Acta Cryst. (2005). C61, o70-o72 [doi:10.1107/S0108270104031385]

The isomeric compounds nimbolide and isonimbolide

K. Anand Solomon, R. Malathi, S. S. Rajan, G. Anitha, J. Josepha Lourdu Raj, S. Narasimhan, G. Suresh and Geetha Gopalakrishnan

Abstract: Nimbolide [systematic name: (4 [alpha] ,5 [alpha] ,6 [alpha] ,7 [alpha] ,15 [beta] ,17 [alpha] )-7,15:21,23-diepoxy-6-hydroxy-4,8-dimethyl-1-oxo-18,24-dinor-11,12-secochola-2,13,20,22-tetraene-4,11-dicarboxylic acid [bold gamma] -lactone methyl ester], C₂₇H₃₀O₇, was isolated from the leaves of Azadirachta indica, and its isomer, isonimbolide [systematic name: (4 [alpha] ,5 [alpha] ,6 [alpha] ,7 [alpha] ,15 [alpha] )-7,15:21,23-diepoxy-6-hydroxy-4,8-dimethyl-1-oxo-18,24-dinor-11,12-secochola-2,16,20,22-tetraene-4,11-dicarboxylic acid [bold gamma] -lactone methyl ester], was prepared from a novel rearrangement reaction of nimbolide, using boron trifluoride etherate and tetrabutylammonium bromide. The reaction conditions are probably responsible for the ether cleavage, double-bond rearrangement and reformation of the ether linkage. As a result, there are conformational changes in two cyclopentane rings and the side-chain -CH₂COOMe group. In isonimbolide, an $R_{4}^{4}$ (24) hydrogen-bond motif is observed.

Formula: Two isomers of C₂₇H₃₀O₇


	Structure factor file (CIF format) (129.7 kbytes) Contains datablock I

	Structure factor file (CIF format) (185.6 kbytes) Contains datablock II

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