Lactones aldol” ring cleavage

Dendrobine, a congener of the powerful convulsant picrotoxinin, was first isolated from the Chinese tonic Chin Shih Hu in 1932, but its complete structure was not unravelled until 1964. Three groups of workers have reported the synthesis of dedrobine since that time. The synthesis outlined below was developed by Kende and his group at Rochester, and is based on the c/s-hydroindan nucleus (B) derived from the Diels-Alder adduct (A) by cleavage and aldol cyclization. The hydroindan derivative (B) already carrying the isopropyl unit, bears appropriate functionality for elaboration of the N-methylpyrrolidine ring and the 7-lactone moiety. 

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