K. Nishitani et al., TOTAL SYNTHESIS OF (PLUS-OR-MINUS)-CIS-CEMBRANOLIDES, TRANS-CEMBRANOLIDES AND (PLUS-OR-MINUS)-SARCOPHYTONIN-B FROM GERANYLGERANIOL, Heterocycles, 37(2), 1994, pp. 679-681
(+/-)-cis-Cembranolide (I) was synthesized via Cr(II) mediated intramo
lecular macrocyclization of omega-formyl-beta-methoxycarbonylallyl hal
ides (6a and b), which were prepared starting from geranylgeraniol. Th
e stereoselective synthesis of (+/-)-trans-cembranolide (II) was achie
ved by lactonization of 14-membered cis-intermediate (7) with inversio
n of the stereochemistry at C-2. (+/-)-Sarcophytonin B (III) was also
synthesized from (+/-)-cis-cembranolide (I) via isomerization of the e
xo-cyclic double bond.