ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
(1RS, 5SR)-2,2,5-Trimethylcyclopentane-1-carboxylic acid (17) and (1r, 2RS, 5SR)-1,2,5-trimethylcyclopentane-1-carboxylic acid (19) are the starting materials for the α-alkynone routes to (±)-capnellene and for similar efforts towards ptychanolide. Since 17 and 19 have, so far, been available only by a branching reaction from the same precursor, the cyanohydrin mixture 2/3, a modified synthesis for 17 and a new one for 19 was developed (Scheme 1). The common precursor 2/3 was treated with POCl3 which effected normal dehydration to 6 (47%, major path) in competition with Me migration to 8 and 9 (17%). The minor path to 8 and 9 could be reduced to 3% when SOCl2 was used for the dehydration of 2/3. This reaction was the basis for an improved synthesis of 17 from 1, using the steps b, e, i, r, and v see Scheme 1 in an overall yield of 35%. The POCl3 reaction was also studied with the pure cyanohydrins 2 and 3, the configurations of which were determined by an X-ray analysis of 2. Me migration did not occur form 2 but only from 3 (25%), which has HO—C(1) and H—C(5) in a cis position. With SOCl2, 3 underwent only 5% Me migration. The new synthesis of 19 started with 4 using the steps h, n, p, and s (see Scheme 1) in an overall yield of 68%.
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19860690525
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