Acorane, Carotane, Cedrane, Zizaane

Reagents i, PTSA- N ii, ICHjCCI CH iii, HjOlw, HgCOAclj-BFj-HOAc v, KOH vi, H 

LDA vii, MeCHO viii, PTSA ix, MczCuLi x, HOAc xi, BjHg xii, Na2Cr207 H xiii, h.p.l.c. 

A number of model esters related to lac resin have been prepared. These esters have the basic cedrane skeleton (149) or the C-2 epimeric structure. In an approach to the synthesis of cedrene (152), the intramolecular photocycloaddition of the dienone (150) was carried out at low temperature. A major tricyclic compound (151) was obtained and its structure was verified by X-ray analysis of its anisylidene derivative. Further work is required to bring about the rearrangement of a derivative of (151) to give cedrene. Further details on the hydroxylation (with O3) and chlorination (with PhICl2) of cedrol, patchoulol, and their derivatives have been presented. The results of this study are in keeping with those obtained previously. 

From a careful study of vetiver oil (from the Moosanagar area of North India) Ganguly et al. ° have isolated and identified the two biogenetically important alcohols, (+)-allokhusiol (153) and (—)-khusiol (154). These two compounds co-occur with (-l-)-zizaene (155) and (+)-prezizaene (156), and furthermore it has been shown that (153) gives both (+)-zizaene (155) and (+)-prezizaene (156) on dehydration with phosphorus oxychloride, while treatment of khusiol tosylate with pyridine produces (+)-prezizaene as a minor product. It would also appear from these results that (-)-khusiol is enantiomeric with (-H)-allocedrol isolated by Tomita and Hirose but that (+)-allokhusiol is not the enantiomer of the alcohol identified by Carroll et al.  

NaOH viii, NaH ix, MeMgBr x, CH2N2 xi, SOCla-py xii, LiAIH4 xiii, POClj-py xiv, N2CHC02Et-Bp3 

The absolute stereochemistries of a- and /3-pipitzol have been unambiguously established as (177) and (178) respectively by the chemical transformation of a-pipitzol into (-)-a-cedrene (179) and by X-ray analysis of a-pipitzol benzoate.  

An examination of the minor constituents of Cupressus dupreziana has resulted in the isolation of the three alaskane-type sesquiterpenoids (180)—(182) together with the two 1,7-diepi-cedrane derivatives (183) and (184). In view of the importance of absolute stereochemistry in these and related compounds it is regrettable that the [a]o value of only one of them (183) is quoted. Indeed this is all the more surprising when the comparison of [a]o values has played an important role in the proposals of the same authors to account for the distribution and biogenesis of acorane, alaskane, cedrane, 1,7-diepi-cedrane, 

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