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Conformational Behaviour of 11-O-Methylazithromycin in the Solid and Solution State

Conformational behaviour of azithromycin 11-OMe derivative 2 (Scheme I) has been studied in the solid and solution state. In the CDCl3 and DMSO solution 2 adopts mainly "folded-in" conformation. 11-OMe group is oriented toward the centre of aglycone ring. The crystal structure of DMSO solvate of 2 has been solved by molecular replacement method using solution state conformation as search model. Conformation of 2 in the solid and solution state is very similar. Molecules of 2 are held together in the crystal by Van der Waals interactions forming a solvent chanel along the b axis. The DMSO molecule is found to be disordered and bound to cladinose moiety of 2 by H-bond O4"-H...O1s.

azithromycin; crystal structure; molecular replacement; NMR

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