Synthetic studies of cephalandole alkaloids and the revised structure of cephalandole A.

A synthesis of the originally proposed 2-(1 H-indol-3-yl)-4 H-3,1-benzoxazin-4-one structure of the alkaloid cephalandole A (1) led to a structural revision, and the isolated natural product has now been identified as the previously known compound 3-(1 H-indol-3-yl)-2 H-1,4-benzoxazin-2-one (7). The structural assignment was corroborated by detailed NMR studies. A short synthesis of the related natural compound cephalandole B (2) has also been performed, confirming its structure. In addition some chemical transformations, involving, for example, the related synthetic molecule 2-(1 H-indol-3-yl)-3 H-quinazolin-4-one (9), are presented.