Communicated by John D. Roberts, March 27, 1961. The structure of the .... 'Pople, J. A., W. G. Schneider, and H. J. Bernstein, Can. J. Chem., 35, 1060 (1957).
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phasized that we have not yet proved with certainty that the RNA thus synthesized is an exact replica of the "primer" DNA. Summary.-Experiments are described in which the nearest neighbor to cytidylate and base composition was determined for RNA synthesized by a partially purified bacterial enzyme which requires DNA. The results show that different DNAs alter the position of cytidylate in the newly assembled RNA chain and that the ribopolynucleotide has an average base composition similar to the "primer" DNA used. The authors are indebted to Drs. E. Peter Geiduschek and Alexander Rich for providing the purified salmon and bacterial DNA. * This investigation was supported by funds from the Argonne Cancer Research Hospital and from the Joseph and Helen Regenstein Foundation. t Operated by The University of Chicago for the United States Atomic Energy Commission. 1 Weiss, S. B., and L. Gladstone, J. Am. Chem. Soc., 81, 4118 (1959). 2 Weiss, S. B., these PROCEEDINGS, 46, 1020 (1960). 3 Stevens, A., Biochem. and Biophys. Research Communications, 3, 92 (1960). 4 Hurwitz, J., A. Bresler, and R. Diringer, Biochem. and Biophys. Research Communications, 3, 15 (1960). ' 5 Weiss, S. B., and T. Nakamoto, J. Biol. Chem., 236, PC18 (1961). 6 Josse, J., A. D. Kaiser, and A. Kornberg, J. Biol. Chem., 236, 864 (1961). 7Volkin, E., and L. Astrachan, Virology, 2, 149 (1956). 8 Belozersky, A. N., and A. S. Spirin, Nature, 182, 111 (1958). 9 Yeas, M., and W. S. Vincent, these PROCEEDINGS, 46, 804 (1960). 10 Hall, B. D., and S. Spiegelman, these PROCEEDINGS, 47, 137 (1961). 11 Belozersky, A. N., and A. S. Spirin, in The Nucleic Acids, ed. E. Chargaff and J. N. Davidson (New York: Academic Press, Inc., 1960), vol. 3, p. 147.
FURAZAN OXIDES, I. THE STRUCTURE OF BENZOFURAZAN OXIDE BY FRANK B. MALLORY AND CLELIA S. WOOD DEPARTMENT OF CHEMISTRY, BRYN MAWR COLLEGE
Communicated by John D. Roberts, March 27, 1961
The structure of the compound C6H4N202, which may be obtained by treatment of o-nitroaniline with alkaline sodium hypochlorite or by pyrolysis of o-nitrophenyl azide, has been the subject of controversy since the compound was first recognized in 1894.1 There is still no general agreement on which of the variety of structures, I-VI, that have been proposed2 by different workers since that time is correct.
0
I
II
~~~
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P0
NZO EDE0
lIlaN+
IlIb
PROC. N. A. S.
00
IIIC
IV
V VI The original suggestion' that the compound was o-dinitrosobenzene (I11a) was soon rejected in view of its striking resistance to oxidation2 by several reagents that readily convert nitroso groups to nitro groups. Recently, however, the o-dinitrosobenzene structure has been readvocated,3 with the modification that the canonical forms II1b and IMIc make a large contribution to the proposed hybrid. For a brief time the name Vt-o-dinitrosobenzene was applied to this hybrid structure III,3 but this notation apparently has been abandoned.4 Structures V and VI were proposed2 to account for the lack of properties typical of nitroso compounds and for the fact that only a single compound of formula X-C6H3N202. is obtained from either 2nitro4-X-aniline or 2-nitro-5-X-aniline for various groups X:
NH2 N02 N02 This apparent equivalence of the two positions across the ring from the nitrogen substituents has been interpreted by several workers to indicate a symmetrical configuration for the N202 grouping in this type of compound.5 However, an alternative explanation for this lack of existence of isomers was proposed by Hammick and co-workers,6 who formulated the parent compound as benzofurazan oxide (I). It was postulated that a facile equilibrium exists between the two isomeric substituted benzofurazan oxides by way of a dinitroso compound as a transient intermediate, such that only the more stable furazan oxide would be isolated: NH2
NaOCa -*
~NaOCI
X-C6H3N202
X
0 N
t
FNo
N \
0 o
This quinonoid structure, I, was further supported by the demonstration6 of the addition of bromine to give a tetrabromide, which was formulated as VII. Structure VI, which is also quinonoid, was considered6 to be unlikely since the compound shows no properties characteristic of peroxides.2 Br
BrN
C
N
V CH Br lH Br VII
0
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It is now possible to rule out all symmetrical structures such as III, IV, V, and VI on the basis of the 60-megacycle proton NMR spectrum of the compound in either carbon tetrachloride or deuterochloroform solution. * The spectrum obtained in either solvent shows a complicated pattern of proton resonances, which pattern does not have the symmetry expected7 for the A2B2 arrangement of two pairs of equivalent protons. Two structures remain, I and II, which are consistent with the NMR results. It is felt that structure I is preferable to structure II on theoretical grounds since I should have a considerably larger delocalization energy than II. Structure I contains a system of twelve 7r electrons delocalized over ten nuclei and may be represented as: xN
whereas structure II contains the smaller system of eight ir electrons delocalized over seven nuclei, with the additional energetic disadvantage that the 7r-electron system is non-cyclic. Furthermore, the fact that benzofurazan, whose structure is N
VIII
well-accepted as being VIII, is white (Xmax 300.0 mg, E30O.o 3330 in 95%, ethanol), while the compound here formulated as benzofurazan oxide (I) is yellow (Xmax 355.5 miA, e36z.5 6960 in 95%0 ethanol),8 indicates that the latter contains a larger 7relectron system than benzofurazan and not a smaller one as would be the case if structure II were correct. Thus, it is considered to have been proved that this compound of composition C6H4N202 has structure I and may appropriately be named benzofurazan oxide. Substantiation of this structural assignment is being sought by X-ray crystallographic studies that are now in progress. The furazan oxide structure has also been demonstrated9 to be correct for compounds of the open-chain type (IX). R' N 4
IX
Boyer and Buriks have recently claimed to have demonstrated the existence of two readily interconvertible isomeric forms of this compound C6H4N202 of markedly different polarity on the basis of a separation of the pure compound by paper chromatography.'0 However, repetition of this work has shown that this interpretation is invalid. The observed chromatographic separation depends only on the method of impregnation and development of the chromatogram. It was further established that these separations are artifacts by showing that a sample of
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o-nitroaniline of high purity gave qualitatively the same chromatographic behavior as I under all conditions investigated. A detailed presentation of the reconciliation of all known properties of benzofurazan oxide with its structure, I, will be published shortly. * The spectra were obtained both from Dr. Marjorie C. Caserio of the California Institute of Technology, Pasadena, and independently from Dr. LeRoy F. Johnson of Varian Associates, Palo Alto. This assistance is gratefully acknowledged. 1 Noelting, E., and A. Kohn, Chem.-Ztg., 18, 1905 (1894). 2 For various pertinent references, see J. V. R. Kaufman and J. P. Picard, Chem. Rev., 59, 429
(1959). 3Boyer, J. H., R. F. Reinisch, M. J. Danzig, G. A. Stoner, and F. Sahhar, J. Am. Chem. Soc., 77, 5688 (1955). 4 Boyer, J. H., and S. E. ElIzey, J. Am. Chem. Soc., 82, 2525 (1960). 5Green, A. G., and F. M. Rowe, J. Chem. Soc., 103, 897 (1913); Forster, M. O., and M. F. Barker, J. Chem. Soc., 103, 1918 (1913); see also J. H. Boyer and G. Mamikunian, J. Org. Chem., 23, 1807 (1958). 6 Hammick, D. L., W. A. M. Edwards, and E. R. Steiner, J. Chem. Soc., 3308 (1931). 'Pople, J. A., W. G. Schneider, and H. J. Bernstein, Can. J. Chem., 35, 1060 (1957). 8 Given as X,,,. 355 m/A, C 556910 in ethanol by J. H. Boyer, U. Toggweiler, and G. A. Stoner, J. Am. Chem. Soc., 79, 1748 (1957). 9 Meisenheimer, J., H. Lange, and WV. Lamparter, Ann., 444, 94 (1925); Kinney, C. R., J. Am. Chem. Soc., 51, 1592 (1929). 10 Boyer, J. H., and R. S. Buriks, J. Am. Chem. Soc., 82, 2216 (1960). 0
A CHEMICAL SYNTHESIS OF ISOMALTOSE* BY M. L. WOLFROM, A. 0. PITTET,t AND I. C. GILLAMt DEPARTMENT OF CHEMISTRY, THE OHIO STATE UNIVERSITY
Communicated March 3, 1961
Among the naturally occurring oligo- and polysaccharides, a number of the most interesting compounds contain a-linked D-glucose units. The chemical synthesis of all but the simplest a-D-glucopyranosides has proved to be far more difficult than that of the ,B-D-anomers. The synthesis of a ,f-D-glucopyranoside link is readily achieved' by use of the Koenigs and Knorr reaction2 in which a tetra-Oacyl-a-D-glucopyranosyl halide reacts with a hydroxylic compound, generally in the presence of an acid acceptor. An application of the Koenigs-Knorr reaction to the synthesis of a-D-glucosides has hitherto been of limited success. The known poly-O-acyl-f3-D-glucopyranosyl halides are either unstable and tend to rearrange to the more stable a-D anomeric form or they react with hydroxylic compounds by a mechanism involving participation of the trans 2-0-acyl group in the displacement at C-1 leading to products of f3-D-configuration.3 The ability of the protecting group at C-2 to participate in this manner is believed to play an important role in the readiness with which the halides of the f3-D-series anomerize. The two such compounds of this series which are relatively stable, namely, 3,4,6-tri-O-acetyl-/3-Dglucopyranosyl chloride and 3,4,6-tri-O-acetyl-2-0-(trichloroacetyl)-,8-D-glucopyranosyl chloride,4 are characterized by groups at C-2 which show only a slight tendency to participate.5 6 Thus, Hickinbottom7 was able to prepare, from these halides,
