COMMUNICATIONS 'ro THE EDITOR
May 3, 1962
lloscowitz and Moffitt's case I where the ellipticity curve is simply proportional to the absorption curve.'O The fitted rotatory strengths seem to be in accord with the points enumerated above. We have observed :hat the spectrum of hexahelicene above Z0)O A. red-shifts with increasing hydrocarbon solvent density as do the spectra of other nonpolar polynuclear aromatics. l Thus, if the solvent dependence arises from shifting spectrum, the decrease of rotation cannot be accounted for by red-shifts of the positive Cotton curves. Most likely the decrease depends on a strong redshifting negative Cotton curve centered a t a wave length shorter than 3100 A. Indeed, the m.0. calculation predicts such a rotational strength for a higher energy transition. In addition, the experimental rotatory dispersion measurements of Drs. are consistent Kewman and Tsai out to 2T30 with such a situation. That the change in optical activity arises from distortion of the helical pitch cannot be completely discounted but, to be sure, is not completely separable in theory from the origins of the spectral shift. Certainly this study underscores the usefulness that parallel solvent effect studies on spectra and rotation might have in the interpretation of optical rotatory dispersion curves, especially were the latter measurements carried to the absorbing region. I t also demonstrates what must be a contribution to environmental effects in more complex systems, one observable in the wings of the Cotton curve where nearly all characterizing measurements of protein and polypeptide systems are made,I3 and one not accounted for by the Lorentz field factor. Acknowledgments.-Acknowledgment is made to the donors of the Petroleum Research Fund, administered by the American Chemical Society, for partial support of this research. A grant from the National Science Foundation under its Undergraduate Research Participation Program is also gratefully acknowledged by the participants (E. C. K., N. J. K., a n d T . C. C.).
The chemical shifts of the C-19 methyl groups in the n.m.r. ~ p e c t r a ,together ~ with the known method of infrared analysis near S.4 p j 4can be used to classify the heteroyohimbines into six stereochemical groups (represented by groups -1to F in Table 1).5 Despke the retention of the trans-quinolizidine system, the raunitidine to isoraunitidine isomerization involves only the asymmetric center a t C-3,6.7 since in our hands treatment of isoraunitidine with mercuric acetate and subsequent reduction of the A3-perchloratesalt with sodium borohydride yielded only raunitidine.
e/
D Methiodide salt
/
I1
IIa
B (epiallu)
I
(10) \\'. h I o 6 t t and A . hfoscowitz, J . C h e i i z . Phys., 3 0 , 648 (1959). (11) 0. E. Weigang, Jr., J . Chcin. Phys., 33, 892 (1960). Shifts in polar solvents m a y be treated similarly; 0. E. Weigang, Jr., and D. U. Wild, submitted t o J . Chem. Phys. (12) M S. S e w m a n and Lin Tsai, private communication of unpublished measurements. (13) For several reviews see: (a) I. Tinoco, R. W.Woody and K. Yamaoka, l'eii,ahedioiz, 13, 134 (1961); (b) J. T. Yang, ibid., 13, 143 (1061); (c) B. Jirgensons, itid, 1 3 , 166 (1961); (d) J. Strem, 1 ' . S . R. Krisna-Prasad and J . A . Schellman, i b i d . , 13, 176 (1861); (e) J . R. Fresco, i b i d . , 13, 183 (1961); ( f ) P. 0. P. Ts'o and G. Helmkamp, i b i d . , 1 3 , I98 (1961).
DEPARTMENT OF CHEMISTRY TEXASLUTHERAX COLLEGE SEGUIN,TEXAS
1739
IIIa
C
I11
(ollo) 1, Hg(O.Ac)l
A c d l l \ 2, N a B b
COOCHS
A ' &
N. C. KSETEX
X. J. KRAUSE T. 0. CARMICHAEL 0. E. WEIGASG,JR. RECEIVED J A N U A R22, Y 1962
I
IV
D
IVa
(cpiah)
T H E STEREOCHEMISTRY OF T H E HETEROYOHIMBINE ALKALOIDS
Sir: \Ye here describe the complete stereochemistry of the alkaloids rauniticine, raunitidine, isoraunitidine, mayumbine, and raumitorine.112 (1) E. Wenkert, B . Wickberg and C. 1,. Leight, J . A i n . C'hem. Soc., 83,503i (1Wil). (2) 1 1 , Shamma and J . B. N m s , ibzri., 83, .jO:18 (1
