Synthesis and Analgesic Activity of 4,7-Dimethyl-3,4,4a,5,8,8a-Hexahydro-2-Chromen-4,8-Diols Containing Alkyl-Substituted Aromatic Moieties

A series of new heterocyclic compounds with the hexahydro-2H-chromene skeleton were prepared by reacting the monoterpenoid para-mentha-1,8-diene-5,6-diol with 4-alkyl-substituted aromatic aldehydes. Adding small alkyl substituents (methyl and ethyl) to the aldehyde aromatic ring increased the yields of hexahydrochromenes as compared with the analogous reaction with benzaldehyde. However, adding a branched substituent (isopropyl) and longer butyl and octyl moieties reduced the yields of the target compounds. The stereoselectivity of the reaction changed as the alkyl substituent lengthened. The analgesic activity of the obtained products was studied.