摘要:

AbstractThis paper describes a stereospecific synthesis of nine 2E,6E, 10(Z)‐trienyl esters R1R2CCH(CH2)2CR3CH(CH2)2CR4CHCO2Me (1a‐i) and their selective conversion into the corresponding epoxides(7a‐i), including the natural occurring hormones JHI‐III. The trienyl system of1has been reached stereospecifically by allowing specifically substituted vinylcuprates, [R1R2CCHCuY]⊖, to react with 4‐iodo‐1‐butyne, followed by conversion of the formed enynes R1R2CCH(CH2)2CCH (3) into new cuprates of the type thus [R1R2CCH(CH2)2CR3CHCuY]⊖. These cuprates furnish, upon reaction with 4‐iodo‐l‐butyne, the dienynes R1R2CCH(CH2)2CR3CH(CH2)2CCH (5). From5, vinylcuprates [R1R2CCH(CH2)2CR3CH(CH2)2CR4CHCuY]⊖have been obtained which, upon reaction with carbon dioxide followed by methylation, gave compounds1. For the preparation of the vinylcuprates from the 1‐alkynes we generally used a new alkylcopper(I) s

ISSN:0165-0513    

DOI:10.1002/recl.19811000702

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractThe formation of a 1,2,4‐cyclohexatriene derivative (cf. 7) from the singlet‐excitedcis‐butenyne is thought to be the primary reaction step in the photocyclization of 1,4‐diarylbutenynes. This very reactive intermediate can yield the end‐product along various pathways: (i) directly via a [1,5] hydrogen shift; (ii) via radical intermediates, formed either by acceptance of a hydrogen atom from the solvent (e.g.benzene, hexane) or by release of a hydrogen atom in the presence of oxygen; (iii) via ionic intermediates, formed either by acceptance of a proton (e.g.from methanol) or by release of a proton in the presence of amines. The rates of the cyclization are approximately equal for various butenynes. Differences in product quantum yields are mainly due to differences in the rates of the ring‐opening reaction of the cyclic allene. Using laser flash photolysis two transients of the cyclization could be observed. The effect of amines on the transients i

ISSN:0165-0513    

DOI:10.1002/recl.19811000703

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractIrradiation of 1‐(9‐phenanthryl)‐4‐phenylbutenyne (1) in aprotic solvents containing oxygen gives two products, namely a photocyclization product, 1‐phenyltriphenylene3, as is usually formed from diarylbutenynes, and a photooxidation product (2), derived from cyclopropapyrone. The formation of the latter product is rather specific to the butenyne1.Both products arise from singlet‐ excited butenyne, probably via the same cycloallene intermediate4. Supposedly, this intermediate is converted by triplet oxygen into a 1,2‐dioxetane, having an exocyclic double bond, from which the oxidation product can be formed by ring opening and further rearrangements. The negligible photooxidation of other butenynes is ascribed to the much shorter lifetime of the corresponding c

ISSN:0165-0513    

DOI:10.1002/recl.19811000704

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractReaction ofN1‐substituted uracils with bromine in water at pH 7 leads to 5‐bromo‐6–hydroxy‐5,6‐dihydrouracils. For differentN1‐substituents these products were isolated and the relatively stable derivatives were characterized by1H NMR and mass spectroscopy. On electrophilic iodination with [131I]iodide and chloramine‐T in water no indications were obtained for the formation of such dihydrouracils except for uridine and deoxyuridine. However, on reaction ofN1‐substituted uracils withN1‐iodosuccinimide in CHCl3containing ethanol or in ethanol, 5‐iodo‐6‐ethoxy‐5,6‐dihydrouracils could be

ISSN:0165-0513    

DOI:10.1002/recl.19811000705

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

In the present investigation, we have measured the secondary kinetic deuterium isotope effects in hydroxylamine addition reaction for a series of cyclohexanones, both hindered and unhindered. We observed a slightly direct isotope effect,kH/kD>1.00, for unhindered cyclohexanones and an inverse isotope effect,kH/kD<1.00, for hindered cyclohexanones; this inversion of the isotope effects is attributed to a decrease of the torsional strain through the intervention of an “effet stérique de compression” that induce a slight deformation of the cycle and changes the angle of approach of the nucleop

ISSN:0165-0513    

DOI:10.1002/recl.19811000706

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractThe synthesis of the 5′‐ and 3′/2′‐phosphorylated heptamer sequence pAGCCUGG(3′/2′)p, corresponding to the fragment 14–20 ofE. colitRNAfmet, is described. The assemblage of the fully protected heptamer16was effected via a modified phosphotriester approach which is based on the use of the monofunctional phosphorylating agent, 2,2,2‐trichloroethyl 2‐chlorophenyl phosphorochloridate (3). Thus, various suitably protected building blocks were prepared which were phosphorylated with3on the 3′‐hydroxyl function (e.g.compounds4and5). For the introduction of the 5′‐ and 3′/2′‐phosphate functions, two terminal building blocks were synthesized; one with,inter alia, a 5′‐O‐(phenyl benzyl phosphoroamidate) function (8) and another with 2′‐O‐(diphenyl phosphate) and 3′‐O‐propionyl groups (10). The latter intermediates (i.e.compounds4, 5, 8and10) were assembled to give the fully protected heptanucleotide (16). Complete deprotection of16by

ISSN:0165-0513    

DOI:10.1002/recl.19811000707

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19811000708

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractThe synthesis of the crystalline and easily accessible phosphorylating agent 4‐nitrophenyl 4‐morpholinylphosphonochloridate is reported. Its application to the preparation of 5′‐phosphorylated ribonucleosides (e.g.pA, ppA and pppA) as well as RNA fragments (e.g.pUpU and ppUpU) is demonstrated. Further, special attention is paid to the mild removal of the 4‐nitrophenyl group from fully protected phosphotriester inte

ISSN:0165-0513    

DOI:10.1002/recl.19811000709

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractSulfonation of 11‐methylene‐1,6‐methano[10]annulene (6a) with1, 3, 4 or 6 equivalents of the dioxane‐SO3complex in dioxane results in the formation of the 2‐sulfonic acid (6b) as the exclusive1H NMR detectable product, whereas 1,6‐methano‐[10]annulene (5a) with 3 equiv. of this sulfonating agent already yields the 2,7‐disulfonic acid. The lower reactivity of the peripheral ring of 6a compared with that of 5a is explained in terms of a higher coplanarity of the annu

ISSN:0165-0513    

DOI:10.1002/recl.19811000710

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

Abstract6α‐O‐Methanesulfonylneopine (3b) was converted into 6‐demethoxythebaine (4b) with the aid of potassium tert‐butoxide. Diels‐Alder reaction of 6‐demethoxythebaine with ethyl acrylate yielded mainly 4,5‐epoxy‐6,14‐endo‐etheno‐7α‐ethoxycarbonyl‐3‐methoxy‐17‐methylmorphinan (5b), an intermediate for the

ISSN:0165-0513    

DOI:10.1002/recl.19811000711

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY