Stereoselective synthesis of the basic skeleton of aphidicolan-type diterpenes via intramolecular Diels–Alder cyclisation. Synthetic approach to aphidicoline
The basic tetracyclic skeleton of aphidicolan-type diterpenes has been synthesised by an intramolecularDiels–Alder reaction of 1-(1-cyano-5-methoxy-3-methylbenzocyclobuten-1-yl)hept-6-en-3-one (9). The cyclised product (10) was converted into the tetracyclic compound (11) by treatment with base followed by acid hydrolysis. The stereochemistry of (11) was easily determined from the n.m.r. spectral