Of eremophilone

A second stereoselective total synthesis of ( )-eremophilone (243) has been accomplished using 7-epinootkatone (242) as intermediate.109 The latter compound was synthesized from (—)-/3-pinene (241) by modification of the published procedure"0 and subsequently converted into eremophilone (243) by the series of functional-group transformations shown in Scheme 30. A mycotoxin isolated from Penicillium roqueforti has been assigned the highly oxygenated eremophilane structure (244) on the basis of chemical and spectroscopic evidence."1 The structure and... 

A Bomewhat related instance of double-bond migration initiating epoaide reanrangement is the multiple tranaformation of eremophilone f ide S4 r resented in Eq. (467),... 

Allylic epoxides seem to behave normally. Stereospecific hydride migrations were observed in the McMurry et al. synthesis of eremophilone. Treatment of the isomeric epoxides (268) and (270) under standard conditions resulted in the exclusive formation of the rearranged ketones, as illustrated in equations (114) and (115). 

Reduction of eremophilone, 17, with RhCl(PPh3)3 affords 13,14-dihydroeremophi-lone, 18, whereas supported Pd leads to a more rapid reduction of the conjugated double bond in 19 ... 

However, reaction of tetrahydro-eremophilone with methyl magnesium iodide followed by dehydrogenation gave 7-isopropyl-l,5-dimethylnaphthalene instead of the expected 1,3-dimethyl isomer. Thus, the partial structure of eremophilone should be represented by 60, with the remaining methyl group at one of positions 4, 5 or 7. 

The elucidation of the stereochemistry of eremophilone is bound up with that of HDE and is summarised below. The relative configuration of HDE was obtained from an X-ray diffraction study which showed the cw-decalin system with the methyl, isopropyl and hydroxyl substituents all in an equatorial arrangement as depicted in 57A (52,53). Since pyrolysis of the acetate of HDE yielded eremophilone, both have the same relative and absolute stereochemistry. Attempts to assign the absolute stereochemistry of eremophilone by chiroptical methods led to contradictory results (54-56). The origins of these lay in the use of unsuitable model systems and, therefore, a chemical solution was needed. 

The structure of isoeremophilone 66 was established by correlation with the compound derived from calcium/ammonia reduction of the acetate of 1,11-diene (58). Alloeremophilone (67), also reported as a minor constituent of E. mitchelli, can be generated from the acetate of HDE (57) by pyrolysis, which also yields equivalent amounts of eremophilone (59). 

Robinson R 1939 Cited in Penfold A R, Simonsen J L Constitution of eremophilone, hydrox-yeremophilone and hydroxydiydroeremophilone. III. J Chem Soc 87-89... 

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