982
€1.
c. SRIVASTAVA AND F. S h l I T H
VOl. 79
[CONTRIBUTION FROM THE DEPARTMENT OP AGRICULTURAL BIOCHEMISTRY, UNIVERSITY OF MINNESOTA]
Structure of Corn Hull Hemicellulose. Part V. Partial Hydrolysis and Identification of 4-O-p-D-Xylop yranosyl-D-xylose and 5-0-p-D- Galactopyranosyl-L-ar abof uranos e 'I
B Y H.
c. SRIVASTAVA AND F. SMITH
RECEIVED SEPTEMBER 13, 1956 Partial hydrolysis of corn hull hemicellulose gives in addition to arabinose, xylose, galactose and 2-0- [a-D-glucopyranosiduronic acid]-D-xylose,a number of neutral oligosaccharides. Two of these oligosaccharides have been shown in a previous and 4-O-~-~-galactopyranosyl-~-xylose. Of the communication of this series, to be 3-O-a-~-xylopyranosyl-~-arabinose and 5-O-~-n-galactopyranosyl-Lremaining oligosaccharides, two are shown herein to be 4-O-~-~-xylopyranosyl-~-xylose arabofuranose.
Hydrolysis of corn hull hemicellulose3 with 0.01 amounts of 2,3,4,6-tetra-0-methyl-~-galactose and N hydrochloric acid has been shown previously4 2,3-di-O-methyl-~-arabinose.The former was to give xylose, arabinose, galactose, 2-0- [a-D- identified as N-phenyl-D-galactopyranosylamine glucopyranosiduronic a c i d ] - ~ - x y l o s e ~ together ~~ 2,3,4,6-tetramethyl ethers by melting point, specific with a number of neutral oligosaccharides. Two rotation and by comparison with an authentic of the neutral oligosaccharides were shown to be specimen while the latter was converted to the 3-0-a-D-xylopyranosyl-L-arabinose and 4-O-/3-~-ga- characteristic 2,3-di-O-inethyl-~-arabinose 1,4-bislactopyranosyl-~-~-xylose.~ This paper is con- p-nitrobenzoate. cerned with the isolation and identification of two CH,OR more disaccharides, namely, 4-O-/I-~-xylopyranosylD-xylose (xylobiose) and 5-0-/3-~-galactopyranosylL-arabofuranose (I, R = H). The identification of 4-O-/I-~-xylopyranosyl-~xylose is based upon the following experimental H OR H OR evidence. Upon acid hydrolysis, it gave only 11, R OCH, I,R=H xylose. It had m.p. 184-185' and showed [?ID -30' changing t o -23' (water), constants which From the above results i t may be concluded that are in agreement with the values reported? for a the disaccharide is either 5-O-~-galactopyranosylspecimen of 4-0-/3-~-xylopyranosyl-~-xylose ob- L-arabofuranose (I, R = H) or 4-O-~-galactotained from corncob holocellulose. The xylobiose pyranosyl-L-arabopyranose. A decision between was also recognized as its phenylosazone which these two structures may be reached by applying had m.p. 205' and [ a ] , -50' (pyridine:ethanol). the rules of i ~ o r o t a t i o n . ~ The structure of the hitherto unknown disacThe contribution of the L-arabopyranose residue charide, 5-O-P-~-galactopyranosy~-~-arabofuranose will be highly positive and approximately equal to (I, R = H) rests on the following facts. The the equilibrium value (4-104') observed for Ldisaccharide showed [&ID - 13' (equilibrium value arabinose] whereas that of the L-arabofuranose in water) and gave upon acid hydrolysis galactose residue will be about -40' on the assumption and arabinose as revealed by paper chromatog- that it will be approximately the same as that of raphy. Treatment of I (R = H) with phenyl- 2,3,5-tri-O-methyl-~-arabofuranose. lo Inspection of hydrazine afforded a phenylosazone which upon the glycosides of D-galactopyranose shows that the hydrolysis gave a reducing sugar which was chro- contribution of those of the a-type would be about matographically identical with galactose. This + B O ' while those of the /3-type would be approxiestablished that the arabinose residue constituted mately 0'. Providing that intermolecular interthe reducing end of the disaccharide and also that action has little effect on the contribution of each Cz of the arabinose moiety was not involved in the residue of a disaccharide] i t is possible to make the biose linkage. Methylation of I (R = H) first following approximations. A combination of the with methyl sulfate and alkali and then with L-arabopyranose residue with an equilibrium rotamethyl iodide and silver oxide afforded the fully tion of 104' with the a-D-galactopyranosyl methylated derivative (11, R = OCHs), [a]D-36' residue having [a]D JrlSO' will result in a disacin methanol which gave upon hydrolysis a mixture charide with a high positive rotation (4-120' to ( [ a ] D 4-38' in methanol) of approximately equal 150'). The combination of the L-arabopyranose residue ( 104') with a 0-D-galactopyranosyl resi(1) Paper No. 3582, Scientific Journal Series, Minnesota Agricultural Experiment Station, University of Minnesota. due (4-0') would produce a value for the disaccha(2) This research was done under contract with the United States ride of about 4-50'. The third possible combinaDepartment of Agriculture and authorized by the Research and tion consisting of the L-arabofuranose residue Marketing Act of 1946. The contract was supervised by the Northern ( -40') with the a-D-galactopyranosyl residue Utilization Research Branch of the Agricultural Research Service. (3) M. J. Wolf,M. M. MacMasters, J. A. Cannon, E. C. Rosewall (4-180') would result in a value of about 4-70' and C. E. Rist, Cereal Chem., 80, 451 (1953). while the fourth and last possible combination, (4) R. Montgomery, H. C . Srivastava and F. S m i t h , THISJOURNAL, consisting of the L-arabofuranose residue ( -40') 79, 698 (1957).
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(5) R. Montgomery, F. Smith and H . C . Srivastava, ibid., 78, 2837
(1956).
(6) R. Montgomery, F. Smith and H. C . Srivastava, ibid., 7 8 , 6169 (1856). . . (7) R. L. Whistler and C . C. Tu. ibid.. 74, 3609 (1952).
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( 8 ) J. C . Irvine and D. McNicoll, J . Chem. Soc., 97, 1449 (1910). (9) C. S. Hudson, THISJOURNAL, 51,66 (1909): "Polarimetry, Saccharimetry and the Sugars,'' Circular C. 440 of the Natl. Bur. Standards, by Frederick J. Bates and Associates, 1942, p. 428. (10) S- . Baker and W. N. Haworth. J . Chcm. So
