摘要:

AbstractWhen caryophyllene (1) and isocaryophyllene (2) are irradiated at their π,π*‐ transitions (λ ≤ 253.7 nm) they rearrange relatively rapidly and in high yield to mixtures of isomeric sesquiterpene hydrocarbons. Compounds3–11, the structural determinations of which are described, represent 90% of the photoisomers. All the rearrangements involve the 1, 5‐diene systems, and, with the exception ofcis‐transisomerizations, fragmentation of the doubly allylic σ‐bond and disappearance of the trisubstituted double bond always occur. The cyclopropane, acetylene, allene, and 1, 5‐diene compounds resulting are the first examples of this type of photo‐isomerization products obtained from unconjugated monomeric 1, 5‐dienes by direct excitation with light. Their formation appears to be stereospecific, and is dependent on the stereochemistry of the double bond system in1and2. In addition to thecis‐isomer2caryophyllene yields only compounds3, 4, and5, while from isocaryophyllene, compounds8, 9, 10and11are formed in addition to1. The only isomerization products common to both caryophyllenes (1and2) are6and7. This behaviour and the lack of positive identification of a biradical (triplet) intermediate lead to the probable conclusion that the greater part of the photoisomerization occurs directly from the excited singlet states. Possible mechanisms for the formation of the photoisomerization

ISSN:0018-019X    

DOI:10.1002/hlca.19710540142

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

AbstractThe synthesis of six insulin fragments is described, in which various sequences of the two chains are linked by the disulfide bridge between A20and B19. The fragments in question are: A20–21–B19–21, A20–21–B18–21, A20–21–B17–21, A19–21–B19–21, A16–21–B18–21and A20–21–B12–21.In order to build up the simpler fragments the disulfide bridge was established by oxidation with iodine of two S‐trityl cysteine peptides in which the carboxyl and amino groups were protected by thet‐butyl andt‐butyloxycarbonyl residue. From the mixture obtained the unsymmetrical cystine peptide was separated in all cases from the two symmetrical ones by counter‐current distribution.In the synthesis of the more complex fragments advantageous use was made of smaller unsymmetrical fragments prepared as above but having one amino group protected by the N‐trityl residue. After selective elimination of this group it was possible to lengthen the peptide chain at this position.The free peptides were obtained by removal of the protecting groups with strong acids, in particular concentrated hydrochloric acid. While in this deprotecting step the disulfide bond was stable, conditions are discussed under which disproportionation was observed.None of the six synthetic insulin fragments showed activity in stimulating rat adipose tissue

ISSN:0018-019X    

DOI:10.1002/hlca.19710540143

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

ISSN:0018-019X    

DOI:10.1002/hlca.19710540144

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

ISSN:0018-019X    

DOI:10.1002/hlca.19710540101

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY