5290
H.
[CONTRIBUTION FROM
THE
RAPOPORT,
H. D. BALDRIDGE, JR.,
AND
E. J. VOLCHECK, JR.
VOl. 75
DEPARTMENT OF CHEMIWRYAND CHEMICAL ENGINEERING,UNIVERSITY OF CALIFORNIA, AND THE NAVAL MEDICAL RESEARCH INSTITUTE ]
The Lactone Ring of Carpaine BY
HENRYRAPOPORT, HENRYD. BALDRIDGE, J R . , ~AND EMILJ.
VOLCHECK, JR.
RECEIVED JUNE 22, 1953 Although carpamic acid is not attacked by periodate, it is oxidized by lead tetraacetate, indicating the presence of a 1,2aminoalcohol structure. This is confirmed by isolation of 12-ketotetradecsnoic acid from the oxidation of nitrogen-free inaterial obtained from degradation of methyl N-methylcarpamate methiodide. The hydroxyl group of carpamic acid is thus at the D'-position 111, and carpaine has the structure 1'1.
acid a t 25' and PH 8 was treated with a periodate solution, no oxidation occurred. Since it has been shown4 that periodate oxidation of amino alcohols probably involves the free amine, and since carpamic acid, in which the nitrogen has a PKa of 10.42,exists only to the extent of 0.4% as the free base a t PH 8, this oxidation was repeated a t pH 8.9 and 10.2. Again no measurable oxidation was observed. A t higher temperatures oxidation did take place, but it was indiscriminate and of no structural significance. (N,J--d---(CH?)?-C=O C H II ~J'(CH2h ~ : Carpamic acid was then treated with lead tetraacetate and was found to undergo oxidation at 25". I I1 One mole of oxidant was smoothly consumed in 30 In considering the various positions in the piperi- hours, after which consumption continued but a t a dine nucleus for the terminus of the lactone ring, slightly slower rate, a behavior frequently encountwe f i s t examined the hydrolysis product of car- ered with aminoalcohols.4 I n attempting to isopaine, carpamic acid (111). This substance is an late acetaldehyde from the reaction mixture, volaaminoalcohol, and the hydroxyl group must reside tile aldehydic material was obtained, but since a similar behavior was observed from a solution containing only lead tetraacetate, this attempt was abandoned. A possible rationale for the resistance of carpamic CHI
