摘要:

AbstractThe four‐membered cyclic nitrones (2,3‐dihydroazete 1‐oxides)1a‐gisomerize to the corresponding oximes3and4on treatment with potassiumtert‐butoxide. InN,N‐dimethylformamide at room temperature, oxime4is formed preferentially; in tetrahydrofuran, both the oximes3and4are formed. The oximes3c‐eare converted into the corresponding 6H‐1,2‐oxazin‐6‐ones5c‐eby reaction in acetic acid. The oxime4ahas the (E,E) stereochemistry and theO‐benzoyl derivative of3b (6)the (Z,E) stereochemistry, as shown by X‐ray analysis. In solution, NOE difference spectroscopy indicates the (Z,E) and (E,E) configuration for3aand4a, respectively. The α,β‐unsaturated ketone (Z)‐8was prepared by reaction of (Z,E)‐3bwith bispyridine silver permanganate. Reaction of (Z)‐8with hydroxylamine in pyridine yields (Z,E)‐3band the 6H‐1,2‐oxazin‐6‐one5b, which is formed by rapid cyclization of (Z,Z)‐3b.The conversion of nitrones1into the corresponding oximes3and4is explained in terms of an electrocyclic ring opening of an intermediateN‐hydroxy‐1,2‐dihydroazete. In this electrocyclic reaction, a strong preferenc

ISSN:0165-0513    

DOI:10.1002/recl.19861050402

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe title compound (4) was prepared starting from 17β,19‐dihydroxyandrosta‐4,6‐dien‐3‐one 17,19‐diacetate (5). Copper‐catalyzed conjugate addition of methylmagnesium iodide gave, after hydrolysis, 17β,19‐dihydroxy‐7α‐methylandrost‐4‐en‐3‐one (8a), which was converted by oxidation and deacylation into 7α‐methylestr‐5(10)‐ene‐3,17‐dione (11). Selective protection of the 3‐keto group as the dimethyl acetal, followed by ethynylation and deacetalization, gave the desired product4.The 7β‐methyl adduct, a by‐product in the Grignard reaction, was removed after the oxidation step. Its structure was confirmed by an inde

ISSN:0165-0513    

DOI:10.1002/recl.19861050403

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractTwo spin‐labelled dinucleotide derivatives and two spin‐labelled trinucleotide derivatives have been prepared and their constitution established using HPLC and enzymatical degradation.1H NMR spectroscopy was performed prior to and after reduction of the spin label with ascorbic acid. 2‐(tert‐Butylsulphonyl)ethylN6‐(diphenylacetyl)‐5′‐O‐(4,4′‐dimethoxytrityl)‐2′‐deoxyadenosyl phosphoromorpholidite (4) was prepared and used for the phosphitylation ofN6‐(diphenylacetyl)‐3′‐O‐levulinoyl‐2′‐deoxyadenosine (7) to give the dinucleotide derivative8and the trinucleotide derivative10.The spin label was introduced in the 5′‐position of these compounds, using (5), to give compounds9and11in the fully protected form.Unexpectedly, the stability of the spin label was found to be so high that the function could be used as the definite blocking for the 3′‐hydroxyl group in the 2′‐deoxyadenosine moiety. Thus, starting from3and using compound5, 2‐(tert‐butylsulphonyl)ethylN6‐(diphenylacetyl)‐2′‐deoxy‐3′‐adenosyl 1‐oxyl‐2,2;6,6‐tetramethyl‐4‐piperidinyl phosphate (6) was obtained. This compound afforded the protected di‐ and tri‐nucleotide derivatives12and13, following one or two phosphitylations with4and subsequent oxidation.Deprotection of the derivatives9,11,12and13to the

ISSN:0165-0513    

DOI:10.1002/recl.19861050404

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractHydrogenation of methyl linoleate on palladium catalysts in solution with tetraalkylammonium perchlorate as electrolyte, leads mainly to the saturated product methyl stearate. At negative potentials of the catalyst electrode controlled at about − 1 Volt versus a saturated calomel electrode (SCE) with negligible current passage, the monoenic intermediate is the end product, with the double bond found mainly in theZconfiguration at the starting 9‐ and 12‐positions. As expected it was found that methyl oleate was not hydrogenated by the catalyst held at − 1.1 Volt, while smooth hydrogenation occurs under identical conditions when the catalyst potential is not controlled. Methyl linolenate leads mainly to dienoic esters at − 1.8 V catalyst potential. The effect was applied on a synthetic scale in the hydrogenation of soya bean oil with palladium catalysts, resulting in a considerable increase of selectivity at negative catalyst p

ISSN:0165-0513    

DOI:10.1002/recl.19861050405

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe effect of impregnating metal on carbon catalysts with liquid films, immiscible with the bulk solvent, on rate and selectivity in liquid‐phase hydrogenations has been investigated. Both acid and alkaline films have been used with benzene and phenol as the reactant. The bifunctional character of such catalysts has been demonstrated and a substantial improvement in selectivity for the hydrogenation of phenol to cyclohexanone has been achieved. The factors contributing to the observed phenomena in such multiphase catalytic reactions are discusse

ISSN:0165-0513    

DOI:10.1002/recl.19861050406

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

Abstract4‐O‐Acetyl‐1,6‐anhydro‐3‐O‐(4‐methoxybenzoyl)‐β‐D ‐mannopyranose was converted in two steps into 4‐O‐acetyl‐1,6‐anhydro‐2‐deoxy‐2‐phthalimido‐β‐D‐glucopyranose. Trimethylsilyl tri‐fluoromethanesulphonate‐catalysed coupling of 1,6‐anhydro‐2,3‐O‐(4‐methoxybenzylidene)‐β‐D‐mannopyranose with 1,3,4,6‐tetra‐O‐acetyl‐2‐deoxy‐2‐phthalimido‐β‐D‐glucopyranose, followed by treatment with 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone, afforded the title compound. After triflation, the disaccharide thus obtained was treated with lithium azide or potassium phthalimide to afford 4‐O‐(3,4,6‐tri‐O‐acetyl‐2‐deoxy‐2‐phthalimido‐β‐D‐ glucopyranosyl)‐1,6‐anhydro‐2‐azido‐3‐O‐(4‐methoxy‐benzoyl)‐2‐deoxy ‐β‐D‐glucopyranose and 4‐O

ISSN:0165-0513    

DOI:10.1002/recl.19861050407

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19861050408

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19861050409

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19861050401

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY