摘要:

The proton magnetic resonance spectra ofD-xylose,D-lyxose,D-arabinose,D-ribose,D-glucose,D-mannose, andD-galactose were determined at 100 Mc.p.s. in deuterium oxide. The chemical shifts and structures of a number of ring protons in these compounds were determined either by spin-decoupling experiments or by synthesis of specifically deuterated compounds. The proton magnetic resonance parameters are shown to provide considerable information on the conformations and tautomeric equilibria for the sugars in aqueous solution. It is concluded that, for aldopyranoses in a chair conformation, the chemical shift of equatorial protons at a given position is virtually independent of configurational changes at other positions. However, an axial proton is shielded about 0.3 p.p.m. less by an axial hydroxyl group at a neighboring position than when the hydroxyl group is in an equatorial orientation. An axial hydroxyl group leads to deshielding of an opposing axial proton by about 0.35 p.p.m. By using the chemical shifts of the ring protons of β-D-xylopyranose and β-D-glucopyranose as reference point, the chemical shifts of protons in other pyranose structures could be anticipated to within a useful degree of accuracy.Evidence was obtained thatD-ribose and 2-deoxy-D-ribose exist in aqueous solution both in the pyranose and in the furanose forms. None of the other pentoses showed readily detectable amounts of the furanose forms at equilibrium. AlthoughD-allose does not give readily detectable amounts of the furanose forms when at equilibrium in aqueous solutions,D-altrose does.D-Talose showed only two forms, one of which was the β-pyranose structure.

ISSN:0008-4042    

DOI:10.1139/v66-037

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Previous work on the oxidation of alkyl phenols with peroxy radicals is summarized. The yields of the peroxy-cyclohexadienones formed from 2,6-di-t-butyl-4-methylphenol in the α,α′-azo-bis-isobutyronitrile-initiated oxidation of tetralin at 40 °C have been measured quantitatively. The results suggest that not all the oxidation chains are initiated by isobutyronitrile peroxy radicals.The products from the oxidation of 2,6-di-t-butylphenol and 2,6-dimethyiphenol with (butyl peroxy radicals are found to be mainly dialkyl-p-benzoquinones and tetraalkyl diphenoquinones.

ISSN:0008-4042    

DOI:10.1139/v66-038

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Ten products from the oxidation of 2,4-di-t-butylpheuol witht-butyl peroxy radicals have been identified. They can be subdivided into three groups, depending on the type of radical–radical coupling reaction by which they are produced or in which their precursors are formed: (i) phenoxy–peroxy coupling, (ii) phenoxy–phenoxy coupling at the 6 positions, and (iii) phenoxy–phenoxy coupling through the oxygen atom of one radical and the 6 position of the second radical. Products resulting from still other phenoxy–phenoxy coupling reactions are undoubtedly formed in minor amounts.

ISSN:0008-4042    

DOI:10.1139/v66-039

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Epimerization of 4-oxa-3-oxo-5α-cholestane by Brewster and Kucera's method gave only a 23% yield of the 5β-lactone; several other compounds were formed, apparently via skeletal rearrangement during hydrolysis of the tosylate. The attempted epimerization of 4-oxa-3-oxo-5β-cholestane gave mainly unsaturated acids, but no 5α-lactone (a small amount of skeletal rearrangement also occurred). Both epimers undergo rearrangement to γ-lactones when treated with trifluoroacetic acid.Mass spectra, used in conjunction with infrared and nuclear magnetic resonance spectra and other data to make structural assignments, were found to be highly sensitive to certain structural features. In particular, they can usually distinguish sharply between molecules that contain a pendant ring structure and those that do not.

ISSN:0008-4042    

DOI:10.1139/v66-040

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Reaction of aromatic nitrile oxides with methanesulfonyl and benzylsulfonyl chlorides in the presence of triethylamine yielded sulfonate esters of α-chloroaldoximes. Under the same reaction conditions, aldoximes yielded sulfonate esters, which decomposed to nitriles, and amidoximes yielded amidoxime O-sulfonates, which were also prepared by the action of ammonium hydroxide on. Chemical as well as nuclear magnetic resonance spectroscopic evidence confirms the formulafor amidoximes.

ISSN:0008-4042    

DOI:10.1139/v66-041

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

The Japp–Klingemann reaction has been employed to prepare six new tryptamines. Data on the intermediate phenylhydrazones, β-carbolines, and tryptamine carboxylic acids are presented. Syntheses of 5-methyl-, 6-methyl-, 5,5-dimethyl-, and 5,6-dimethyl-2-oxopiperidine-3-carboxylates are described.

ISSN:0008-4042    

DOI:10.1139/v66-042

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

A general method for selective N-methylation of substituted tryptamines is described. The method involves the lithium aluminium hydride reduction of an intermediate carbamate. Eleven new tryptamines and 11 new carbamoyltryptamines are described.

ISSN:0008-4042    

DOI:10.1139/v66-043

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

The H and13C spectra of vinylene carbonate have been studied by double-resonance techniques. It was found thatJ(13C—H) = ±220.15 ± 0.15 c/s,J(13C—C—H) = ±17.47 ± 0.12 c/s, andJ(H—C—C′—H′) = ±1.47 ± 0.03 c/s. A long-range coupling of 9.26 ± 0.10 c/s was observed between the carbon nucleus of the carbonate group and the vinyl protons. The magnitudes and signs of the geminal13C—C—H couplings are discussed in terms of the molecular orbital theory of Pople and Bothner-By.

ISSN:0008-4042    

DOI:10.1139/v66-044

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Purified cholla gum (Opuntiafulgida) containsL-arabinose (51.6%),D-galactose (31.7%),D-xylose (15.0%),L-rhamnose (2-3%), andD-galacturonic acid (11.2%). Partial hydrolysis of the gum by cold acid produced a polymer which contained onlyD-galactose andD-galacturonic acid in the proportion 9:2. Methylation and hydrolysis of the degraded gum produced 2,3,4,6-tetra-O-methyl-D-galactose (2 moles), 2,3,4-tri-O-methyl-D-galactose (1 mole), 2,4,6-tri-O-methyl-D-galactose (2 moles), 2,4-di-O-methyl-D-galactose (4 moles), and 2,3,4-tri-O-methyl-D-galacturonic acid (2 moles). Smith-type degradation of the degraded gum producedD-galactose (6 moles), glycolaldehyde (? moles), glycerol (2.5 moles), and glyceronic acid (2.5 moles).Hydrolysis of the undegraded gum produced an aldobiouronic acid, which was proved to be 3-O-(β-D-galactopyranosyl uronic acid)-D-galactose by its reduction, methylation, and the identification of the methylated sugars obtained by the hydrolysis of the octamethyl galactobioside.Based on these results, a possible structure for the average chain length of the degraded gum has been proposed.

ISSN:0008-4042    

DOI:10.1139/v66-045

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

With 1,3-dimethyluracil and 1,3,6-trimethyluracil as models for nucleic acid bases, it was found by infrared spectroscopic methods that the site of protonation is a carbonyl group. Analysis of other evidence makes it likely that it is the carbonyl group in position 4. In 1,3,6-trimethyluracil salts, activation of the 5 position under acid conditions permits ready hydrogen–deuterium exchange.Some anomalous 2 base – 1 acid salts with complex acids are considered in the light of base pairing errors in nucleic acids.

ISSN:0008-4042    

DOI:10.1139/v66-046

出版商:NRC Research Press    

年代:1966

数据来源: NRC