Five bicyclo-[3.3.0]octa-2,6-dienes

Abstract

A series of five compounds containing the bicyclo-[3.3.0]octa-2,6-diene skeleton are described, namely tetra-methyl cis,cis-3,7-dihydroxy-bicyclo-[3.3. 0]octa-2,6-diene-2,4-exo,6,8-exo-tetracarboxyl-ate, C16H18O10, (I), tetra-methyl cis,cis-3,7-di-hydr-oxy-1,5-dimethyl-bicyclo-[3.3.0]octa-2,6-diene-2,4-exo,6,8- exo-tetra-carboxyl-ate, C18H22O10, (II), tetra-methyl cis,cis-3,7- dimethoxybicyclo-[3.3.0]octa-2,6-diene-2,4-exo,6,8-exo-tetra-carboxyl-ate, C18H22O10, (III), tetra-methyl cis,cis-3,7-dimeth-oxy-1,5-dimethyl-bicyclo-[3.3. 0]octa-2,6-diene-2,4-exo,6,8-exo-tetra-carboxylate, C20H26O10, (IV), and tetra-methyl cis,cis-3,7-diacetoxy-bicyclo-[3.3.0]octa-2,6-diene-2,4-exo,6,8- exo-tetra-carboxyl-ate, C20H22O12, (V). The bicyclic core is substituted in all cases at positions 2, 4, 6 and 8 with methoxy-carbonyl groups and additionally at positions 3 and 7 with hydroxy [in (I) and (II)], methoxy [in (III) and (IV)] or acet-oxy [in (V)] groups. The conformations of the methoxy-carbonyl gr