ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The racemic spirosesquiterpenes β-acorenol (1), β-acoradiene (2), acorenone-B (3) and acorenone (4) (Scheme 2) have been synthesized in a simple, flexible and highly stereoselective manner from the ester 5. The key step (Schemes 3 and 4), an intramolecular thermal ene reaction of the 1,6-diene 6, proceeded with 100% endo-selectivity to give the separable and interconvertible epimers 7a and 7b. Transformation of the ‘trans’-ester 7a to (±)-1 and (±)-2 via the enone 9 (Scheme 5) involved either a thermal retro-ene reaction 10 → 12 or, alternatively, an acid-catalysed elimination 11 → 13 + 14 followed by conversion to the 2-propanols 16 and 17 and their reduction with sodium in ammonia into 1 which was then dehydrated to 2. The conversion of the ‘cis’-ester 7b to either 3 (Scheme 6) or 4 (Scheme 7) was accomplished by transforming firstly the carbethoxy group to an isopropyl group via 7b → 18 → 19 → 20, oxidation of 20 to 21, then alkylative 1,2-enone transposition 21 → 22 → 23 → 3. By regioselective hydroboration and oxidation, the same precursor 20 gave a single ketone 25 which was subjected to the regioselective sulfenylation-alkylation-desulfenylation sequence 25 → 26 → 27 → 4.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19770600727
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