Cembrene, C20H32, is a diterpene hydrocarbon isolated from pine resin. Cembrene has a UV absorption at 245 nm, hut dihydrocembrene (C20H34), the product of hydrogenation with 1 equivalent H2, has no UV absorption. On exhaustive hydrogenation, 4 equivalents H2 react, and octahydrocembrene, C20H40, is produced. On ozonolysis of Cembrene, followed by treatment of the ozonide with zinc, four carbonyl-containing products arc obtained: Propose a structure for Cembrene that is consistent with its formation from geranyl-geranyldiphosphate.

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нес оно * ронорна Сно ненснснсн, CнассH,CH2CнснснHз CHзсCH-CH2CH CHзссно НСCH-CH CHз