ISSN:0165-0513    

DOI:10.1002/recl.19941130102

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractCarba analogues1, 14, 15and16of Strigol were synthesised in which the vinyl ether oxygen is replaced by methylene. Compound1was prepared by the Wittig reaction of ylid2with aldehyde3. Compounds14, 15and16, for which this approach failed, were prepared by reaction of aldehyde20with lactones17, 18and19, respectively, using the method ofTanakaet al.35,36, or with phosphonates32and33, in a Wittig‐Horner reaction. Subsequent oxidative elimination of the thioether moiety gave the desired product

ISSN:0165-0513    

DOI:10.1002/recl.19941130103

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractHomochiral (αMe)Leu/Ala and Leu/Ala model peptides were synthesized by solution methods and fully characterized. A solution conformational analysis of the tripeptides was carried out using FT‐IR absorption and1H NMR. The crystal‐state structure of Z‐D‐(αMe)Leu‐(D‐Ala)2‐OMe monohydrate was resolved by X‐ray diffraction. The results obtained support the conclusion that the tendency of the non‐coded (αMe)Leu residue to fold into β‐bends and helical structures is markedly higher than that of its unmethylated pr

ISSN:0165-0513    

DOI:10.1002/recl.19941130104

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe facile synthetic approaches to 3‐pyridinecarbonitriles are described. The first approach involves the base‐catalyzed transformation of 4‐hydroxy‐1,1‐cyclohexanedicarbonitrile2ainto4a, b. The other route involves the base‐catalyzed multi‐step one‐pot reaction of aryl methyl ketones with the appropriate arylidenemalononitriles6, 11a, b. Careful study of the synthesis of2a, bfrom1a, brevealed the importance of controlling the reaction conditions. Thus, 1,7‐dioxo‐4,4‐heptanedicarbonitriles3a, bor 3‐pyridinecarbonitrile4awere obtained in addition to the desired2a, bunder dif

ISSN:0165-0513    

DOI:10.1002/recl.19941130105

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractProtection of the exocyclic amino groups of both nucleobases adenine and guanine with theN,N‐dimethylformamidine and cytosine with the isobutyryl group presents a convenient and economical N‐protective‐group‐strategy for the solid‐phase synthesis of DNA fragments containing methylphosphonate linkages at predetermined locations. Thus, the post‐synthesis removal of the N‐protective groups with hydrazine hydrate (16 h at 20°C) afforded immobilized fragments, which were then cleaved from the solid support and deprotected at the phosphorus by treatment with ammonia in methanol (2 h at 20°C) to yield high

ISSN:0165-0513    

DOI:10.1002/recl.19941130106

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe synthesis and spectroscopic characterization of six novel chemically modified retinals, is described, prepared by a single strategy: all‐E‐10,12‐ethanoretinal (1), all‐E‐10,12‐propanoretinal (2), all‐E‐10,12‐ethano‐20‐norretinal (3), all‐E‐20‐nor‐10,12‐propanoretinal (4), all‐E‐12,14‐ethano‐20‐norretinal (5), and all‐E‐20‐nor‐12,14‐propanoretinal (6). For this strategy we developed two novel synthons, 2‐(diethoxyphosphinyl) hexanedinitrile and 2‐(diethoxyphosphinyl) heptanedinitrile which were prepared in their deprotonated form from hexanedinitrile and heptanedinitrile. Bacterioopsin was incubated with each of 1 to 6. Only 1 and 3 form bacteriorhodopsin analogues (bR‐1 and bR‐3). bR‐1 shows light‐dark adaptation and an approx. 50% light‐driven proton‐pump action. bR‐3 does not show light‐dark adaptation or proton‐pump action. It is also shown that the protein can efficiently accommodate retinal with the 10,12‐ethano group whereas the correspo

ISSN:0165-0513    

DOI:10.1002/recl.19941130107

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe reaction of several 2,2,3,3‐tetrasubstituted‐gem‐bromohalocyclopropanes with t‐BuOK in DMSO unexpectedly yielded the monohalocyclopropanes in good yield. A closer investigation revealed that this reaction must be initiated by a nucleophilic attack by the dimsyl anion (CH3SOCH3) on bromine with subsequent protonation of the carbenoid intermediate. The reaction occurs rapidly (within 2 minutes) and is not inhibited by radical scavengers or in the dark. Only bromine, and not chlorine, is reduced, and the intermediate cyclopropyl anion is configurationally stable under the reaction con

ISSN:0165-0513    

DOI:10.1002/recl.19941130108

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe NMR spectroscopy data for five hydroformylation catalysts RhH(CO)2(P‐P) (P‐P = diphosphite bidentate ligand) are reported and interpreted in terms of equatorial and axial coordination of the phosphorus and carbon monoxide ligands in a trigonal bipyramidal struct

ISSN:0165-0513    

DOI:10.1002/recl.19941130109

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19941130101

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY