Synthesis of muscothiazoles A and B: Critical role of methyl group substitution in RCM-based syntheses of macrocycles.

ABSTRACT

[reaction see text] Muscothiazoles A (2b) and B (2c) have been prepared by two approaches that differ in the order of assembly of the rings. Comparative studies show that substitution of the carbon chains in substrate 5 or 12 (respective precursors to 13-membered and 14-membered rings by RCM), even by a single methyl group, can have a profound effect on increasing the efficiency of the macrocyclization.