INFLUENCE OF METHOXY- AND METHYL-AROMATIC SUBSTITUENS ON STEREOCHEMISTRY OF THE PRODUCTS IN THE ACID-CATALIZED CYCLIZATION OF 2-(2-ARYLETHYL)-1,3,3-TRIMETHYLCYCLOHEXANOLS: STEREOCONTROLLED TOTAL SYNTHESIS OF (+/-)- NIMBIDIOL AND (+/-)-NIMBIOL

Article abstract of DOI:10.1016/S0040-4020(01)86225-6

The distributions of the trans- and the cis-podocarpatrienes (5c-g) and (6c-g) in the cyclialkylation reaction of the easily accesible cyclohexanols (4c-g) under a mild condition have been investigated.The cyclohexanol precursors having unactivated aromatic ring proceeds with high stereoselectivity leading to the respective trans-products, while the substrates with an electron donating methoxy or a methyl substituent with respect to the site of electrophilic attack result in the corresponding cis- and the trans-product mixtures.Consistent mechanisms for these stereochemical results have been advanced.Based on these results simple synthesis of the modified diterpenes (+/-)-nimbidiol (7) and (+/-)-nimbiolmethylether (18) have been realized.