ISSN:0165-0513    

DOI:10.1002/recl.19811000202

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractThe complexation of rare‐earth ionsviz. La(III), Pr(III), Nd(III), Sm(III), Gd(III) and Y(III) with thioformohydroxamic acid has been investigated potentiometrically at 30 ± 1°C in a 70 per cent (v/v) dioxane/aqueous medium at 0.1 M ionic strength using theBjerrum‐Calvintitration technique. Stepwise and overall stability constants of all the complex species formed are reported. The values obtained by other methods such as Least Square,BlockandMcIntyre, Schroderand pointwise calculation are in reasonable agreement with theBjerrum‐Calvinhalf‐integral method. The stability order for 1:1 metal‐ligand chelate is found to beSm>N

ISSN:0165-0513    

DOI:10.1002/recl.19811000203

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

Twenty five cyclic and α‐cyclic thioketones were examined by mass spectrometry. Compared with the oxygen analogues, the thioketones yielded a higher proportion of molecular ions. The loss of •SH was found to be a characteristic fragmentation of cyclic and α‐cyclic thioketones as for aliphatic thio

ISSN:0165-0513    

DOI:10.1002/recl.19811000204

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractThe calculation of the enthalpy of activation for the interconversion of the equi‐energetic chair conformers of all‐cis‐1,2,3,4,5,6‐hexamethylcyclohexane (1), using five empirical force fields, gives rather poor results. A sizable negative entropy of activation, indicated by the calculations, can only partly compensate for the differences between experimental and calculated values of the free enthalpy of activation. Comparison of individual strain components with similar data for cyclohexane indicates the importance of the non‐bonded interactions for the interconversion barrier. The barriers for the chair‐chair interconversions of cyclohexane and1should be included in future force field param

ISSN:0165-0513    

DOI:10.1002/recl.19811000205

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

Abstract[Homohistidine2]LH‐RH has been synthesized by the solid phase method. NMR and CD spectra at two pH values have been measured. The remarkably lowin vitropotency of the component, relative to LH‐RH, is discussed in terms of conformational differen

ISSN:0165-0513    

DOI:10.1002/recl.19811000206

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractThe fast, selective and mild removal of levulinoyl groups with hydrazine from galactose, which also carries hydroxyl functions protected with acetyl groups, enabled us, under Koenigs‐Knorr conditions, to synthesize tri‐ and tetrasaccharides containing β‐linked galactose and glucose units. Selective acylation of the primary alcoholic group of the partially protected galactose derivative13bwith levulinic acid was achieved in good yield. The preparation of tetrasaccharide18b, having a free hydroxyl function, was effected by condensing dimer16bwith the bromo derivative17, followed by the removal of the levulioyl group with hyd

ISSN:0165-0513    

DOI:10.1002/recl.19811000207

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractA synthesis of α,β‐dehydroamino acid derivatives12is described, which is of possible general applicability and might be useful for the preparation of peptides which have such a moiety in their sequence. In addition, several didehydrodioxopiperazines (13–17) have been prepared. The reactivity of these compounds towards liquid H2S in the presence of ZnCl2has been studied. Only the dehydroalanine derivatives12aand13gave α‐addition products; all other dehydroamino acid derivatives and cyclic dipeptides failed to react

ISSN:0165-0513    

DOI:10.1002/recl.19811000208

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractCNDO/2 calculations were performed on pentaco‐ordinated phosphorus intermediates which are involved in the reaction of c‐

ISSN:0165-0513    

DOI:10.1002/recl.19811000209

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19811000201

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY