A simple convergent and general method has been developed for the synthesis of (f)-isopisiferin (1 c), a rearranged abietane diterpene, having a hexahydrodibenzo[a,d]cycloheptene ring system, and the related model systems (la) and (lb), through the respective enolisable tricyclic ketone mixtures (12c) and (13c), (12a) and (13a), and (12b) and (13b), obtained from the corresponding easily accessible 2-arylethyl-3,3-dimethylcyclohexanones (7c), (7a), and (7b). Demethylation of the styrenoid ethers (15b) and (15c) under acid conditions gave the tetracyclic dienones (17b) and (17c) through Ar,-5 cyclisation.The recent structural elucidation 'J of isopisiferin (lc), pisiferanol (2), and a number of related compounds, isolated from the seeds of Chamaecyparis pisifera (Cupressaceae), along with the earlier reported phenols, pisiferin (34) and barbatusol (3b),5 represent an interesting group of rearranged 9(1& 20)-abeo-abieta-8,11,13-triene diterpenoids. Recently, the total syntheses of ( + )-pisiferin (3a) and (+)-barbatus01 (3) ' have been reported. We present here the first total synthesis of (+)isopisiferin (lc) and the related model compounds (la) and (lb) by a simple and general convergent route.. .
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