- The Synthesis of Trimethylcyclopentane-carboxylic Acids
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(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 (47percent, major path) in competition with Me migration to 8 and 9(17percent).The minor path to 8 and 9 could be reduced to 3percent 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 35percent.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 from 2 but only from 3 (25percent), which has HO-C(1) and H-C(5) in a cis position.With SOCl2, 3 underwent only 5percent 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 68percent.
- Solaja, Bogdan,Huguet, Joan,Karpf, Martin,Dreiding, Andre S.
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p. 1163 - 1171
(2007/10/02)
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- SYNTHESIS OF A STEREOISOMER OF PTYCHANOLIDE
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A stereoisomer of ptychanolide 1 was synthesized by a method which includes an α-alkynone cyclization.
- Huguet, Joan,Karpf, Martin,Dreiding, Andre S.
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p. 4177 - 4180
(2007/10/02)
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