摘要:

dl-Dimethylbis-p-(2-amino-2-carboxyethylphenyl)silane, which contains two molecules of phenylalanine connected by a dimethylsilyl bridge in the para position, anddl-p-(dimethyl-p-tolylsilyl) phenylalanine were prepared by using the malonic ester synthesis.

ISSN:0008-4042    

DOI:10.1139/v67-405

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The iodination of adrenochrome by iodine is subject to general base catalysis. This is in accord with the view that the rate-determining step in this reaction is the removal of the C-7 proton in the adrenochrome. The order of catalytic activities of the various ions is phosphate > bicarbonate > propionate > acetate, which is also the sequence of the pKavalues of the corresponding acids. However, the catalytic efficiencies of the hydrogen phthalate and phthalate anions are about 10 times greater than those predicted from the dissociation constants of the acid. This is rationalized in terms of an alternative electrophilic–nucleophilic catalysis of the iodination reaction.

ISSN:0008-4042    

DOI:10.1139/v67-406

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The conformational equilibria oftrans-1,4-dibromo- (I),trans-1,4-dichloro- (II), andtrans-1,4-bromochloro-cyclohexane (III) were determined by integration of the separate axial and equatorial proton signals at low temperature. Thevalues for compounds I, II, and III were found to be approximately 200 cal/mole.

ISSN:0008-4042    

DOI:10.1139/v67-407

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

A series of 2-benzyloxytetrahydropyrans bearing substituents at the ortho, meta, and para positions of the benzene ring have been synthesized. From the nuclear magnetic resonance spectrum of each compound, the geminal coupling constant (J) between the non-equivalent protons of the benzylic methylene group was determined. The geminal coupling constant for the methylene group of several benzyl sulfoxides was also measured. In the ether series it was found thatJvaried from 11.1 to 13.3 c.p.s. and was directly proportional to the Hammettσvalue for the meta and para substituents. In the sulfoxides, however,Jwas unaffected by the substituent. On the basis of the molecular orbital theory of geminal coupling constants and steric considerations, it is proposed that the sensitivity ofJto the substituent effect is dependent upon the conformation of the molecules with respect to the Ar—CH2bond. The potential utility of this relation as a method of conformational analysis is discussed.

ISSN:0008-4042    

DOI:10.1139/v67-408

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

A linear correlation of the geminal coupling constants of benzylic protons with the Hammettσconstants has been observed. The proton–proton coupling was made observable by preparing the tetrahydropyranyl ethers of benzyl alcohols. The introduction of the asymmetric center caused the benzyl protons to become non-equivalent. The observed correlation serves as an additional confirmation of the Pople and Bothner-By theory of geminal coupling.

ISSN:0008-4042    

DOI:10.1139/v67-409

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Benzoylation of benzyl β-l-arabinopyranoside with 2.2 molar equivalents of benzoyl chloride gave benzyl 2,3-di-O-benzoyl-β-l-arabinopyranoside (65–70%) and benzyl 2,3,4-tri-O-benzoyl-β-l-arabinopyranoside (10–15%). Benzyl α-d-xylopyranoside, under similar conditions, gave benzyl 2,4-di-O-benzoyl-α-d-xylopyranoside (45%), benzyl 2,3-di-O-benzoyl-α-d-xylopyranoside (27%), benzyl 2,3,4-tri-O-benzoyl-α-d-xylopyranoside (15%), and benzyl 2-O-benzoyl-α-d-xylopyranoside (9%). Several new derivatives of benzyl β-l-arabinopyranoside and benzyl α-d-xylopyranoside have been prepared. These benzoates lead to the ready preparation of 4-O-substitutedl-arabinose andd-xylose derivatives. These results are compared with those obtained for the selective benzoylation of hexopyranosides.

ISSN:0008-4042    

DOI:10.1139/v67-410

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

A general synthetic procedure leading to cyclic hydrogen phosphites has been devised. The effect of solvent on the P==O and P—H infrared stretching modes of cyclic hydrogen phosphites and thiophosphites has been studied. It is concluded that association of cyclic hydrogen phosphites is attributable to dipole–dipole interactions rather than to hydrogen bonding.

ISSN:0008-4042    

DOI:10.1139/v67-411

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The synthesis of three new cyclic hypophosphate systems from 2,2-dimethylpropane-1,3-diol is described. Evidence concerning the presence of the P—P bond in the cyclic hypophosphate and cyclic dithiohypophosphate was obtained by chlorinolysis.In addition, the reactions between 2-ethoxy-5,5-dimethyl-1,3,2-dioxaphosphorinan and 2-chloro-2-oxo-5,5-dimethyl-1,3,2-dioxaphosphorinan and between 2-hydroxy-5,5-dimethyl-1,3,2-dioxaphosphorinan and 2-chloro-5,5-dimethyl-1,3,2-dioxaphorinan are discussed as possible routes to cyclic hypophosphates.Several characteristic features of the infrared spectra of cyclic hypophosphate systems, related compounds, and their acyclic analogues are indicated.

ISSN:0008-4042    

DOI:10.1139/v67-412

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The buffered hydrolysis of 4β-ethyl-4α-methylcholest-5-en-3β-yl mesylate and 4α-ethyl-4β-methylcholest-5-en-3β-yl mesylate has been studied. Both reactions resulted in a predominance of ring-contracted products accompanied by small, but significant, amounts of products derived from stereospecific alkyl shifts. A chair–boat equilibrium is postulated to explain these results.

ISSN:0008-4042    

DOI:10.1139/v67-413

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The nuclear magnetic resonance spectra are reported for a series of α-substituted 3-pentanones. Magnetically nonequivalent methylene hydrogens are observed whenever the substituent group is diamagnetically anisotropic. The results are discussed in terms of the possible conformations of the molecules; the most stable conformations are those with the C=O bond essentially eclipsed by the terminal methyl groups.

ISSN:0008-4042    

DOI:10.1139/v67-414

出版商:NRC Research Press    

年代:1967

数据来源: NRC