5929
RU(NH~)~N 3+ O during the initial phase of the reaction. bered ring alkaloids (i.e., I1 + I).4 This latter process would imply that Aspidosperma alkaloids of type 11 are If HNOz and R u ( N H ~ ) ~form ~ + the same intermediate as R u ( N H ~ ) ~ and ~ +NO, we must conclude that the usual fate of the intermediate is decomposition to R u ( N H ~ ) ~ ~ + and NO, rather than formation of R U ( N H ~ ) ~ N O ~ + . The ion Ru(NH3);N03+ is also formed from RuCOOCHl (NH3):OHz3+with NO. The reaction is of a rapidity I, R = H 11, R = H comparable to that of Ru(NH3):Br 2+ or R u ( N H & ~ + 111, R = CH, IV. R = C u 3 as the starting materials. The rate of formation of VI,, R r H. 6.7-double bond Os(NH3):N03+ (the NO stretching band of [Os(NH&NO](C101)3in KBr is split: weak at 1895; strong, sharp biosynthetic precursors of type I. In order to obtain at 1875 cm-I) from O S ( N H ~ ) : , O H and ~ ~ + NO seems to information on the relationship, if any, between these be even somewhat greater. alternatives we have initiated some studies in Vinca When Fe(CN)63- in excess acid is treated with NO, minor L., a plant which possesses a wonderful array of the yellow solution slowly begins to turn brown. At Aspidosperma alkaloid^.^ the end of 24 hr, the solution is red-brown. Upon A detailed investigation involving the incorporation addition of S2- ion, the solution immediately turns of ~ ~ - t r y p t o p h a n - 3 - 'into ~ C V . minor L. over different violet. This result is consistent with that of Schwarztime intervals was undertaken, and some of the results kopf,8 who claimed that he obtained nitroprusside on are summarized in Table 1. The method involved bubbling ferri- or ferrocyanide solutions with nitric oxide. Table I. Results of Incorporation of ~ ~ - T r y p t o p h a n - 3 ~ ~ C Further work is in progress on these and related reacinto Vinca minor L. at Various Time Intervals tions of ruthenium and osmium. Total incorporation --. Acknowledgments. Financial support for this reVincadine (I) + Vincadifformine search by the National Institutes of Health, Grant No. vincaminoreine (11) + minovine G M 13638-03 and G M 13797-02, and the National Time (111) (4 (IV) (4 BIA Science Foundation, Grant No. G P 5322 X1, is grate4 hr 0.003 0.057 19 fully acknowledged. 1 day 0.015 0.24 16
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(8) P. Schwarzkopf, Abhandl. Deut. Naturw., Med. Ver. Bohhmen, 3, l ( l 9 1 1 ) ; Chem. Abst., 8, 1106 (1914).
John N. Armor, Hans A. Scheidegger, Henry Taube Department of Chemistry, Stan,ford Unicersity Stanford, California 94305 Receiced July I I , 1968
Studies on Indole Alkaloid Biosynthesis.
11'
Sir : In a previous communication' we reported some of our results relating to the later stages of indole alkaloid biosynthesis. In particular it was suggested that the transannular cyclization of nine-membered ring intermediates as had been previously postulated* was probably not a biosynthetically significant reaction in the Aspidosperma and Iboga series. This communication describes further results which strongly support such a suggestion, at least in the Aspidosperma alkaloids, and which in addition yield novel information about the later steps in the biosynthesis of these alkaloids. In the hope of obtaining more distinctly positive results to those reported previously' we have studied a completely different approach to this problem. It is clear that the transannular cyclization process as illustrated in the conversion of the alkaloid vincadine (I) to vincadifformine (11), a reaction easily accomplished in the laboratory,3 is only one of a number of alternative pathways in the plant elaboration of Aspidosperma alkaloids. An equally attractive and plausible scheme could invoke the reverse process, namely the ring opening of the pentacyclic system to yield the nine-mem(1) Part I : J. P. Kutney, W. J. Cretney, J. R. Hadfield, E. S. Hall, 90, 3566 (1968). (2) E. Wenkert, ibid., 84, 98 (1962). (3) J. P. Kutney, I
