M. Mackay, P. Mitrprachachon, P. J. Oliver
May 15, 1985
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Abstract
Orthorhombic, P212121, Z = 4 , 2(CuKa) = 1.5418/k, T = 290 (1) K. Supinine: M r = 283.4, a=10 .068 (1 ) , b=11 .644(1 ) , c = 1 3 . 0 8 6 ( 1 ) A, U = 1534.1 (2)/k 3, Din(flotation) = 1.23 (1), D x = 1.230 Mg m -3, F(000) = 616, a(Cu Ka) = 0.64 mm -l. Heleurine: M r = 297.4, a = 9.269 (1), b = 11.175 (1), c = 16.345 (2) A, U='1693.0 (3)/k 3, Dm(flotation) -1.18 (1), D x = 1.167 Mg m -3, F(000) = 648, /t(Cu Kct) = 0.60 mm -1. Full-matrix least-squares refinement converged at R values of 0.041 and 0.048 for 1411 and 1367 reflections of supinine and heleurine respectively. The absolute molecular structures have been assigned by comparison with that of the aminoalcohol, supinidine. Both alkaloid molecules adopt similar extended conformations which differ from that of intermedine, a retronecine alkaloid also containing 0108-2701/85/050722-04501.50 the trachelanthic acid moiety, by an approximate twofold rotation about the C(1)-C(9) bond. Consequently, in supinine and heleurine the carbonyl group is antiparallel with the C(8)-H(8) bond whereas in intermedine it is synparallel. Introduction. The two alkaloids, monoesters of the amino-alcohol supinidine (I), have been isolated from Heliotropium europaeum L. (Culvenor, 1954), supinine being only a minor product; the latter was however isolated from H. supinum L. as one of three major bases (Crowley & Culvenor, 1959). As in the retronecine monoester, intermedine, the acid moiety in supinine (II) is (+)-trachelanthic acid; the acid moiety in heleurine (III) is (-)-heliotric acid as in the heliotridine monoester, heliotrine (Bull, Culvenor & © 1985 International Union of Crystallography M. F. MACKAY, P. MITRPRACHACHON, P. J. OLIVER AND C. C. J. CULVENOR 723 Dick, 1968). Methylation of the hydroxyl substituent at C(13) in supinine produces heleurine. The analyses reported here are the first reported for a supinidine alkaloid. The results define the effect on conformation of the monoester alkaloids when there is no hydroxyl substituent on the pyrrolizidine nucleus at C(7), and form part of a conformational study of hepatotoxic pyrrolizidine alkaloids. . ~ H20H ,9OH CH3 H~, ! "! OR