Gossypium Cadinanes and Their Analogues: Synthesis of Lacinilene C, 2,7-Dihydroxycadalene, and Their Methyl Ethers

Article abstract of DOI:10.1021/jo00175a007

The total synthesis of lacinilene C methyl ether <1-hydroxy-4-isopropyl-7-methoxy-1,6-dimethyl-2(1H)-naphthalenone> has been accomplished in ten steps with an overall, optimal yield of 38percent by starting with o-methylanisole.Formation of the key α-aryl-α-ketol functionality, which is particularly sensitive to oxidation, was accomplished by stepwise oxidation reactions based on the use of N-methylmorpholine N-oxide/osmium tetraoxide acting on alkene and trimethylsilyl enol ether functionality.Other oxidations could be accomplished by using dichlorodicyanobenzoquinone to generate unsaturation adjacent to the α-ketol group or to form substituted naphtalenes.These reactions permitted adjustment of the oxidation level and oxygenation pattern of the key intermediate, 7-methoxy-α-calacorene (3,4-dihydro-4-isopropyl-7-methoxy-1,6-dimethylnaphthalene), to accomplish the synthesis of 2-hydroxy-7-methoxycadalene, 2,7-dihydroxycadalene, 7-methoxycadalene, and 7-hydroxycadalene, in addition to lacinilene C and its methyl ether.