J. Org. Chem. 1987,52, 1475-1477
1475
Stereospecific (Methylenecyclopropy1)acetyl-CoAInactivation of General Acyl-CoA Dehydrogenase from Pig Kidney John E. Baldwin*' and David W. Parker Departments of Chemistry, Syracuse University, Syracuse, New York 13244,a n d University of Oregon, Eugene, Oregon 97403 Received S e p t e m b e r 17, 1986
An efficient synthesis of racemic methylenecyclopropaneacetic acid has been developed. A mixture of the corresponding diastereomeric coenzyme A esters, one of which is the metabolite of t h e nonprotein amino acid hypoglycin from Blighia sapida directly responsible for its hypoglycemic potency, reacts stereospecifically with general acyl-CoA dehydrogenase from pig kidney to irreversibly inactivate the enzyme.
The amino acid hypoglycin A found in unripe ackee fruit (Blighia sapida) which causes Jamaican Vomiting Sicknessz4 is (+)-cr-amino-2-methylenecyclopropanepropionic acid. It is metabolized by rats through transamination to methylenecyclopropanepyruvic acid followed by oxidative decarboxylation to (R)-2-methylenecyclopropaneaceticacid (MCPA).&' The coenzyme A thioester of MCPA irreversibly inactivates pig kidney general acyl-CoA dehydrogenase;* MCPA-CoA may thus be a "suicide" substrate directly responsible for hypoglycin toxicity.
4CH2."'
Scheme I
2
1
Y
5
3: R = THP 4: R = H
---COOH 4 C H 2 C O O H
~ H ~ C O - S - C O A I
H
H
H
H
hypoglycin A
MCPA
MCPA-COA
Extensive experimental work over the past 35 years directed toward elucidating hypoglycin's activity and molecular mechanism of action has invariably depended upon limited supplies of naturally derived material. An interest in methylenecyclopropane chemistry"" has led us to begin work on the molecular mechanism of this inactivation process, addressing initially this severe and long-standing impediment to detailed mechanistic investigations. The obstruction posed by a limited availability of MCPA from natural hypoglycin has now been circumvented through development of a convenient synthesis of racemic methylenecyclopropaneacetic acid and the corresponding diastereomeric coenzyme A thioesters.
Results and Discussion Racemic methylenecyclopropaneacetic acid was prepared through an efficient four-step sequence of reactions (Scheme I). Addition of the carbene derived from 1,ldichloroethane and n-butyllithium in hexaneslZto 1, the (1) Syracuse University. (2) Hill, K. R. West Indian Med. J. 1952, I, 243-264. (3) Stuart, K. L. In Hypoglycin; Kean, E. A., Ed.; Academic: New York, 1975; pp 39-44. (4) Tanaka, K. In Handbook of Clinical Neurology; Vinken, P. J., Bruvn. G. W.. Eds.: Elsevier/North Holland: Amsterdam. 1979: Vol. 37 (II),
