This type of derivative involved the use of trityl chloride and gives a derivative where all the hydroxyl groups except the primary ones are blocked by an acyl group, usually acetyl. Monomeric sugar derivatives will be considered first, to be followed by polysaccharides, since with the latter there are factors involved which introduce complications. . Formation of quaternary salts was found94 to proceed most readily with pyridine and its p- or 7-substituted derivatives; less readily with a-substituted pyridines; and only slightly with tertiary alkyl- or aralkyl-amines such as triethylamine, diethylaniline, and N-methylmorpholine. Thus; the polysaccharide dextran is formed from sucrose by enzyme preparations from Leuwno~toc~~ while the polysaccharide levan is pro- duced from sucrose or raffinose by enzymes of other ba~teria.
An excellent review of the chemistry of the carbohydrate components of the cardiac glycosides appeared in 1945 in Volume I of this series,1s2and consequently only developments in this subject since that date will be included in the present account. Levene and T i p ~ o n ' ~emphasize ' the fact that both epimers are formed in this reaction but usually one predominates to such an extent that from a practical point of view the other epimer may be disregarded. Extrusion Column Chromatography on Cellulose, M. Wolfrom monograph , Scientific Re- port Series, No. A comparison of the relative activation of pancreatic amylase by a number of anions is given in Table I.
Despite difficulties in estimating exact couplings from theory, the magnitudes of observed, vicinal, spin-spin coupling-constants can often be employed to differentiate between various conformational possibilities and to provide a measure of conformational equilibria in s o l ~ t i o n. These results are in accord with the more rapid decrease in the viscosities and with the more rapid appearance of the achroic point with the amylase of Aspergillus oryzae than with pancreatic amylase. Moffett, and Bernard Wildi, J. The free guanine formed was converted to insoluble xanthine, due to the presence of guanase in the enzyme preparation. See a-Man- 214 26 methyl, 66, 67 acetal, 8, 26 8 nosidwe, 61, 66 8-D-Mannopyranoside, ethyl 1-thio-.
Cellulose nitrate, I, 325, 326; 11, 280; 111, 190, 213, 218, 225 salt effect on, I, 317 Cellulose sulfonates, I, 321 Cellulose p-toluenesulfonate, I, 321 Cellulose xanthate, 11, 280 Celluloses, acid hydrolysis of, V, 109-120 -, commercial regenerated, degree of polymerization, V, 106 -, crystalline and non-crystalline regions of, V, 109-126 -, esterification and etherification, V, 122-124 -, oxidation by periodate, V, 121 -, relative crystallinity of, V, 103-126 -, swelling and density of, V, 107, 120, 121 Cellulosic fibers, density of, V, 121 Celtrobionic acid, I, 44 Celtrobiose, I, 44 8-glucosidase action on, V, 61 orthoesters of, I, 91 Celtrobiose, hexaacetyl-, 1,2 or 1,6-orthoacetic acid, I, 92, 112 e-Celtrobiose, acetochloro-, I, 44, 76 -, heptaacetyl-, and E t 2 0 compound, I, 76 -, octaacetyl-, two forms, I, 76 crystalline molecular compound with pceltrobiose octaacetate and EtlO, I, 76 337 8-Celtrobiose, monohydrate, I, 76 heptaacetate-, and Et,O compound, I, 76 -, hexaacetyl-, 1,2+rthoacetate? Con- versely, relatively small changes in these ratios in amylase solutions before and after various procedures are often taken as proof that only one amylase is present. Hanes, New Phytologist, 36, 101 1937. The engineering schedule in the senior year was such that there would have been no time to continue the work with Professor Evans, but, with the connivance ofWilliam E. These differences were considered to arise from an important structural factor, and the observations led to the first attempt to classify sugar derivatives according to the orientation of the a and P anomeric hydroxyl groups relative to the strainless pyranoid ring, that is, according to what are now known as the axial and equatorial dispositions. The photo- graph in Fig. .
I n the D-aldohexose group, these originally rare sugars are allose, altrose, gulose, idose, and talose. The courses were un- inspiring, much disorganization resulted from the influenza epidemic, and he disliked the barracks life and the snobbish fraternity system of the school. It was hydrolyzed completely to fermentable sugar by beta amylase and corresponded to 100 % amylose by potentiometric titration. Andrews he found the University, old in years and proud of its tradition of learning, suffering from lack of buildings and equipment for scientific research. A good example of how the rearrangement may be used to check structure is the constitutional synthesis of lactose and 136 P. Alfred Gottschalk, The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia.
Further evidence for the formation of intermediate compounds in catalytic reactions is afforded by the observation a that optically active camphor is formed from optically inactive racemic camphor carboxylic acid in the presence of the d- or 1-forms of quinine, quinidine or n i c ~ t i n e ; ~ and b that optically active bases, e. This transformation has been studied further by Lindberg, using hydrogen bromide and mercuric bromide in benzene,? Furanoid Sugar Derivatives in Solution. جهت دریافت اسامی کتابها به سایت زیر مراجعه کنید. Hudson is also remembered for the so-called Hudson's rules, concerning the of sugars. The reason for this might be the general preoccupation with the development of suitable methods for the exact determination of the action of pectic enzymes, which in turn is the result of our lack of knowl- edge of the exact structure of pectic substances.
Proceedings of the Fourth International Congress of Biochemistry, Vienna, Sept. If, in the foregoing reaction of glycosyl bromides, the methanol is replaced by moist acetone, exchange of the bromide ion for hydroxyl takes place. Advances in Carbohydrute Chemistry, Vol. ~ ~ The chloride ion is the most effec- tive anion but it is possible to activate pancreatic amylase with several other anions. Anhydrides of the Pentitols and HexitolsI.
In view of the resemblance in reactivity of sulfonyloxy groups to that of Lalogen substituents, formation of an intermediate di-halogeno derivative may, in some cases, not even be a necessary step. Acetals and Ketals of the Tetritols, Pentitols and Hexitols; Chapter 6. It stands indeed today a monument to the inestimable services of this distinguished Principal and Vice-Chancellor. The preparation of alkyl 2-desoxyglycosides from glycals has already been described, and the same products have also been obtained from desoxysugar mercaptals by the procedure of Pacsu and Green. Maltitol, l,banhydro, 18 8-Maltopyranoside, phenyl 1-thio-, heptaacetate, 18, 27 Maltose, from starch by pancreatic amylase, 235, 247-250 271 by amylase of A spergillus oryzae, 250- by amylase of malted barley, 255-265 a-Maltose, 1-phosphate, 71 Mandelonitrile, catalytic formation of optically active, 53 Mannan, presence in alpha cellulose, 275 0-Mannide, 217 Manninotriose, 66 Mannitan.