A tetrahydropentaleno[1,6a-a]naphthalen-4(2H)-one of defined relative stereochemistry for use towards Agariblazeispirol C

Abstract

Towards the synthesis of the novel natural product Agariblazeispirol C, (5aR*,11bR*)-9-methoxy-3,8,11b-trimethyl-5,6,7,11b-tetrahydro-1H-pentaleno[1,6a-a]naphthalen-4(2H)-one, C(20)H(24)O(2), has been prepared at a key stage of the preparative programme. The structure shows the desired stereochemical outcome of the central cyclization protocol, viz. a syn-relationship between the aliphatic methyl group on the 11b-position and the methylene group on the 5a-position [C-C-C-C = -34.57 (18) degrees ].