Preparation of N-Monoalkyl and O-Acyl Derivatives of Allosamidin, and Their Chitinase Inhibitory Activities

Allosamidin (1) was converted to demethylallosamidin (2) and didemethylallosamidin (3) by a reaction with methylamine and ammonia, respectively. In the same way, a series of N-monoalkyl derivatives was prepared from 1 and 2. A variety of 6- and 6″-O-acyl derivatives of 1 was also prepared by chemically selective acylation. The inhibitory activity of each of these derivatives on chitinases originating from insects and fungi showed that a monomethylaminooxazoline or dimethylaminooxazoline structure was important for strong activity, and that the 6″-O-acyl derivatives of 1 each retained relatively high activity.