Angucyclinones related to ochromycinone. IV - The structures and reactionsof unusual diels-alder adducts formed from maleic anhydride and racemic 5,5-dimethyl-3-vinylcyclohex-2-en-1-ol

The Diels-Alder reaction between maleic anhydride and racemic 5,5-dimethyl- 3-vinylcyclohex-2-en-1-ol gives two racemic diastereomers, the major produc t (2a,S,3R,8aS,8bR)-7,7-dimethyl-2-oxo-2a,3,4,6,7,8,8a,8b-octahydro-2H-benz o[cd]isobenzofuran-3-carboxylic acid (63% yield), and the minor product (2a R,3S,8aS,8bS)-7,7-dimethyl-2-oxo-2a,3,4,6,7,8,8a,8b-octahydro-2H-benzo[cd]i sobenzofuran-3-carboxylic acid (9%). Epoxidation of the major product gives racemic (1aS,3R,3aS,5aR,8aS,8bR)-7,7-dimethyl-4-oxoperhydrobenzo[cd]oxiren o[2,3-e]isobenzofuran-3-carboxylic acid in 81% yield, while opening of the epoxide ring gave the trans diol (2aS,3R,5S,5aR,8aR,8bR)-5,5a-dihydroxy-7,7 -dimethyl-2-oxoperhydrobenzo[cd]isobenzofuran-3-carboxylic acid in 58% yiel d. Treatment of the major Diels-Alder product with osmium tetraoxide gave t he cis diol (2aS,3R,5S,5aR,8aS,8bR)-5,5a-dihydroxy-7,7-dimethyl-2-oxoperhyd robenzo[cd]isobenzofuran-3-carboxylic acid in 86% yield. The structures of four products were confirmed by X-ray and n.m.r. methods. None of the produ cts exhibit anticancer activity.