Absolute structure of an N-pentenoyl benzisothiazole

The title compound, (+)-(3aR,6S,7aS)-1-(8,8-dimethyl-2,2-dioxo-1,3,3a,4,5,6,7,7a-octahydro-3a,6-methano-2,1-benzisothiazol-1-yl)-3,4-dimethyl-4-penten-1-one, C 17 H 27 NO 3 S, was isolated as the major product from a copper-mediated conjugate addition reaction, The absolute stereochemistry of the N-pentenoyl side chain was established. The latter is extended and the cyclohexane ring adopts a boat conformation, whilst the benzisothiazole ring is between a half-chair and envelope.