摘要:

AbstractThe synthesis of the all‐transand 9‐cisisomers of 11,14‐imino‐retinal, 13‐demethyl–11,14‐imino‐retinal, 13‐demethyl‐N‐methyl‐11,14‐imino‐retinal, 13‐demethyl‐11,14‐thio‐retinal and 13‐demethyl‐11,14‐etheno‐retinal is described.The interaction of these retinals with bacterioopsin has been investigated. Theall‐transisomers bind to bacterioopsin to form complexes with λmaxvalues around 430 nm. These complexes are stable and do not convert into bacteriorhodopsin analogues. In these complexes the aldehyde group is still present and can be reducedin situusing NaBH4.The fact that these bridged retinals do not form bacteriorhodopsin analogues must be due either to the steric hindrance or to the electronic perturbati

ISSN:0165-0513    

DOI:10.1002/recl.19841030401

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractThe synthesis by the all‐repetitive‐excess‐mixed‐anhydride (REMA) method is described for two analogues of leucine‐enkephalin,viz.[L‐m‐Tyr1]‐ and [D‐m‐Tyr1]‐leucine‐enkephalin, making use of enzymatically resolved (m‐hydroxyph

ISSN:0165-0513    

DOI:10.1002/recl.19841030402

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractTwo syntheses are described of (‐)‐6‐demethoxythebaine (4), both starting from the 6‐O‐mesyl**** derivative2of (‐)‐codeine. Treatment with sodium hydride in toluene gives (‐)‐6‐demethoxythebaine in 60% yield. The preparation via 8β‐bromo‐6,7‐didehydro‐4,5‐epoxy‐3‐methoxy‐17‐methylmorphinan (3), which is obtained from the mesyl derivative with the aid of lithiu

ISSN:0165-0513    

DOI:10.1002/recl.19841030403

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractIrradiation of two racemates of 4,5‐dihydro‐8‐hydroxygermacrene B (2, 3) results, in addition toE‐Zisomerization, in the occurrence of a [1,3]‐C shift. Conformational differences between the diastereoisomers are reflected in a highly stereospecific phot

ISSN:0165-0513    

DOI:10.1002/recl.19841030404

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

Abstract13C NMR low‐temperature investigations have revealed that the dioxaphosphorinane ring,trans‐annelated with a cyclopentane ring (3), prefers an equatorial‐apical alignment in trigonal bipyramidal phosphoranes. However, the13C NMR low‐temperature investigations of the model compound, in which the dioxaphosphorinane ring istrans‐annelated with a tetrahydrofuran ring (4), have shown that the ligand exchange (pseudorotation) in this compound is very fast on the NMR time scale, even at low temperatures. These results are in fairly good agreement with quantum‐chemical c

ISSN:0165-0513    

DOI:10.1002/recl.19841030405

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractOn the basis of modified neglect of differential overlap (MNDO) quantum‐chemical calculations on nucleoside systems, the effect of methylation of adenine on theanti‐synequilibrium is described and an increased stabilization of thesynconformer, due to selective methylation, is calculated. A moderateanti‐synactivation energy has been found in the case of dm3A, dm6A and dm7A, whereas for dm8A a considerably higheranti‐synenergetic barrier exists. The results are combined with stereo model studies and related to biological data. With respect to restriction‐modification systems, special attention is given to the computed stereochemical freedom of the methyl group in dm6A, with a significant preference for thesynconformation in dm8A being found, leading to the suggestion that, out of the various methylated structures studied, only alternating d(m8A‐T) stretches are able to adopt a Z

ISSN:0165-0513    

DOI:10.1002/recl.19841030406

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractThe photochemical behaviour of 4‐phenyl‐1,2‐dihydronaphthalene (8) is similar to that of unsubstituted 1,2‐dihydronaphthalene (1). The main product is the 1‐phenylbenzobicyclo[3.1.0]hex‐2‐ene (10). 3‐Phenyl‐ and 1‐phenyl‐1,2‐dihydronaphthalenes (14and17) behave differently.14is photostable and17yields only theexo‐isomer of 4‐phenylbenzobicyclo[3.1.0]‐hex‐2‐ene, instead of a mixture of theendo‐ andexo‐isomer as would be expected. The different results are probably due to differences in the steric requirements of the first inter

ISSN:0165-0513    

DOI:10.1002/recl.19841030407

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractEight retinals labelled at positions 14 and 15 with13C and/or2H were obtained with>98% chemical purity, 92%13C incorporation, 95%2H incorporation at position 14 and 99%2H incorporation at position 15. (14‐13C)retinal, (15‐13C)retinal and (14,15‐13C2)retinal were synthesized from (2‐13C)‐, (1‐13C)‐ and (1,2‐13C2)acetonitrile, respectively, while for the synthesis of (14‐2H)retinal, C2H3CN was used. Via a three‐step process these retinals were transformed into (14,15‐2H2)retinal, (14‐13C,15‐2H)retinal, (15‐13C,15‐2H)retinal and (14,15‐13C2,15‐2H)‐retinal. Their13C–13C,13C‐2H and13C‐

ISSN:0165-0513    

DOI:10.1002/recl.19841030408

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

Abstractβ‐L‐Riboguanosine 5′‐phosphate (5′pLG) was prepared by transglycosidation of properly protected L‐ribose and guanine derivatives followed by phosphorylation and removal of all protecting groups. Experiments indicated that 5′pDG was selected from a mixture of L and D isomers in template directed oligomer

ISSN:0165-0513    

DOI:10.1002/recl.19841030409

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractThe reaction‐coordinate for degenerate hydride‐transfer between 1,4‐dihydro‐pyridine and the pyridinium‐ion was searched by MNDO calculations. A linear transition‐state (TS) structure is found to be strongly (>16 kcal/mole) preferred over a bent TS. In the former, rotation about the C‐hydride‐C axis occurs unimpeded, thus creating a continuum of linear TS‐structures with ring to ring orientations varying bet

ISSN:0165-0513    

DOI:10.1002/recl.19841030410

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY