A combination of regioselective sulfenylation of monoterpenoids (11) furnishing terminal allylic sulfides (12) and thermal elimination of phenylsulfenic acid from the corresponding sulfoxides constitutes a general method for conversion of the isopropylidene terminus of monoterpenoids to the 1,3-diene system (14). The general applicability of the method was demonstrated on the monoterpenoids possessing various functional groups. Several 1,3-dienes (14) thus obtained were transformed to furan derivatives (16) by photosensitized oxygenation followed by dehydration. Furans (16) were utilized effectively for syntheses of cyclic and acyclic furanoterpenes. Optically active natural evodone (2) was synthesized and the configuration of the asymmetric center was determined as (R) by cyclization of the optically active 4-(2-furyl)-butanoic acid derivative (19) which was prepared from R-(+)-citrone-llic acid (17) by the above sequence of reactions. The analogous cyclization of the furan derivative (16d) gave 6,7-dihydro-4(5H)-benzofuranone derivative (10), a synthetic key intermediate for linderalactone (8) and curzerenone (9). Carbon-carbon coupling of the furan derivative (16e) bearing a terminal allylic sulfonyl group with 3-furylmethyl bromide and trans 4-benzyloxy-2-methyl-2-butenyl bromide followed by reductive desulfonation and deprotection provided dehydrolasiosperman W and a synthetic intermediate (26) for plera-plysillin-2 (4) respectively.