ISSN:0021-2148    

DOI:10.1002/ijch.197400002

出版商:WILEY‐VCH Verlag    

年代:1974

数据来源: WILEY

ISSN:0021-2148    

DOI:10.1002/ijch.197400003

出版商:WILEY‐VCH Verlag    

年代:1974

数据来源: WILEY

摘要:

AbstractFour cyclic peptides of the typecyclo(Pro‐Gly)nwere synthesized and characterized. The peptides arecyclo(L‐Pro‐Gly)2,cyclo(L‐Pro‐Gly)3,cyclo(L‐Pro‐Gly)4, andcyclo(D‐Pro‐Gly‐L‐Pro‐Gly). Aspects of the cyclization reactions leading to these peptides are discussed, particularly with respect to the choice of sequence of linear precursor peptides and effects of elevated temperatures. The cyclic octapeptide,cyclo(L‐Pro‐Gly)4, was isolated as a crystalline complex with sodium thiocyanate. Experimental details of

ISSN:0021-2148    

DOI:10.1002/ijch.197400004

出版商:WILEY‐VCH Verlag    

年代:1974

数据来源: WILEY

摘要:

AbstractThetert‐butyloxycarbonyl group is quantitatively cleaved from N‐blocked amino acids and peptides by applying a known excess of perchloric acid solution in acetic acid to yield protonated amino groups and free perchloric acid. Back titration of the latter with sodium methylate permits accurate determination of thetert‐butyloxycarbonylderivative. The method is rapid and simple since the same reagent serves for both cleavage and determination of thetert‐butyloxycarbony

ISSN:0021-2148    

DOI:10.1002/ijch.197400005

出版商:WILEY‐VCH Verlag    

年代:1974

数据来源: WILEY

摘要:

AbstractPoly‐p‐vinylbenzoic acid was polymerized fromp‐vinylbenzoic acid, and some of its physicochemical properties were studied (infrared and ultraviolet spectrum, solubility, density and refractive index increment in solutions, molecular weight). The polymer was readily transformed to poly‐p‐aminostyrene in a one step reaction by Schmidt transposition, in pure sulphuric acid. Polyampholytes were isolated and characterized at different stages of the

ISSN:0021-2148    

DOI:10.1002/ijch.197400006

出版商:WILEY‐VCH Verlag    

年代:1974

数据来源: WILEY

摘要:

AbstractThe sequential polytripeptide (Lys‐Ala‐Pro)nand the random polypeptide (Lys36.2Ala32.5Pro31.3)nwere synthesized as model histones to be used in studying the structure and interactions of nucleohistone complexes. The CD spectra of (Lys‐Ala‐Pro)nin aqueous solutions, at both pH 7 and 11, as well as in HFIP, TFA, and 1 M SDS (pH 7), indicated that this polytripeptide only assumed the random coil conformation under all these conditions. In aqueous solution, the CD spectra of the random sequence polypeptide indicated that this polymer undergoes a pH‐dependent random coil‐helix transition as the pH is raised from 7 to 11. This polymer was also partially helical in TFE. The observation that the random polymer can assume a regular, asymmetric structure may be due to a clustering of lysyl and alanyl residues at one end of the polymer because of the faster incorporation of Pro than Lys or Ala, as indicated by their respective kinetics of polymerization. The random conformation of the sequential polypeptide, (Lys‐Ala‐Pro)n, is probably determined by the presence of Pro at regular intervals. It is concluded that the sequential polymer (Lys‐Ala‐Pro)nis a plausible model histone for use in studying the influence of amino acid sequence and composition on the structure and interactions of nucl

ISSN:0021-2148    

DOI:10.1002/ijch.197400007

出版商:WILEY‐VCH Verlag    

年代:1974

数据来源: WILEY

摘要:

AbstractAn alternating high‐molecular‐weight polymer of L‐valine and L‐lactic acid was synthesized in the solid state. Results from circular dichroism (CD) and nuclear magnetic resonance (NMR) spectra indicate that these polymers are helical in helicogenic solvents such as chloroform and trifluoroethanol (TFE). The conformational analysis is extended to include semi‐empirical energy calculations for alternating α‐amino and α‐hydroxy acid polymers. Preliminary calculations based on depsipeptides from L‐alanine and L‐lactic

ISSN:0021-2148    

DOI:10.1002/ijch.197400008

出版商:WILEY‐VCH Verlag    

年代:1974

数据来源: WILEY

摘要:

AbstractThe relative first‐order rates of deprotection of N∈‐benzyloxycarbonyllysine in 2%, 10%, and 50% trifluoroacetic acid in dichloromethane at 20° are 1, 50, and 1000, respectively. The N∈‐2‐chlorobenzyloxycarbonyl group is at least 60 times more stable than the N∈‐benzyloxycarbonyl group under solid‐phase conditions, because no branched peptides (<0.2 mole%) were formed during synthesis of decalysylvaline using Nα‐tert‐butyloxycarbonyl‐N∈‐2‐chlorobenzyloxycarbonyllysine. Since O‐2‐chlorobenzylserine, Nim‐tosylhistidine, Nim‐2,4‐dinitrophenylhistidine and S‐4‐methylbenzylcysteine were completely stable in 50% trifluoroacetic acid–dichloromethane for over 200 h, these side‐chain protecting groups should be suitabl

ISSN:0021-2148    

DOI:10.1002/ijch.197400009

出版商:WILEY‐VCH Verlag    

年代:1974

数据来源: WILEY

摘要:

AbstractThe peptidylanthranilic acid ester is stable during the reactions leading to the elongation of peptides. However, when the ester is hydrolyzed, the amide bond of peptidylanthranilic acid is catalytically hydrolyzed at pH 7, owing to the effect of the free carboxyl group of the anthranilic residue, into peptide and anthranilic acid. In this reaction, no decomposition or significant racemization of peptide was observed, and the protected peptide was easily obtained. Only in the case of glycylanthraniloyl derivatives did the rearrangement into peptide and anthranilic acid occur in aqueous solution.

ISSN:0021-2148    

DOI:10.1002/ijch.197400010

出版商:WILEY‐VCH Verlag    

年代:1974

数据来源: WILEY

摘要:

AbstractA review of recent work utilizing photosensitive protecting groups is presented, (literature to September 1973 is reviewed). Although still in the developmental stage, the application of groups such as 2‐nitrobenzyl, 3‐nitrophenyl, 3,5‐dimethoxybenzyl, 2,4‐dinitrobenzenesulfenyl and 3,5‐dimethoxybenzoinyl in synthetic chemistry shows great promise for t

ISSN:0021-2148    

DOI:10.1002/ijch.197400011

出版商:WILEY‐VCH Verlag    

年代:1974

数据来源: WILEY