摘要:

AbstractThe syntheses of compounds14–19, 6‐methyluracilacryloyl derivatives, and27–29, photoreactive aryl azide analogs of the antitumor antibiotic sparsomycin(1)are described. All of the modifications in the 6‐methyluracilacryloyl part of1were achieved by selective reduction or by selectiveN‐ andO‐methylation of6(Scheme 2). The key step in the synthetic scheme to the photo‐affinity analogs is the reaction of the chloromethyl sulfoxides20and21with the properly protected cystamine22in liquid ammonia, to give the sparsomycinN‐protected amines23and24, respectively (Scheme 4). Subsequently, the photoreactive groups,viz. ap‐azidosalicylyl and a 4‐azido‐2‐nitrophenyl group, were coupled with these amines. For an evaluation of the biological activity of the compounds prepared, inhibition of protein biosynthesis in two cell‐free assays, cell‐growth inhibition ofE. coliin liquid medium and inhibition of murine leukemia L1210 colony formation in soft agar were studied. All variations introduced in the “western A” fragment of1render the drug biologically inactive. Apparently, the uracil ring plays an important role in the interaction of sparsomycin with the ribosomal peptidyl transferase and its unmodified presence is crucial for displaying activity. The photoprobes, carrying modifications in the “eastern C” fragment of1, do interact with the ribosome, but less

ISSN:0165-0513    

DOI:10.1002/recl.19921110401

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractThe reductive cleavage of phenylalkylphosphines Ph2PR, PhPR2(R = Bu, iPr) with Na/NH3is unselective: both phenyl and alkyl groups can be cleaved and Birch reduction may occur. Reaction of Ph2tBuP gives a high yield of diphenylphosphide. Polar groups (CO2Na, SO3,Na) at the ω position of primary alkyl groups may lead to an increase in selectivity; Birch reduction is suppressed and a functionalised secondary phosphide is obtained.From diarylbenzyl‐ and diarylallylphosphines, the benzyl and allyl groups are selectively removed; Ar2PH and ArRPH are formed in high yield after hydrolytic work‐up unless the aryl group bears F, CF3, or (CH3)2N substituents. From the reaction mixture of Ph2PCH2Ph we have isolated 1,2‐ ‐diphenylethane.2‐Methoxyphenyl and 2,6‐dimethoxyphenyl groups are selectively removed from Ar2BuP, ArPhBuP and Ar2P(CH2)3PAr2, forming ArBuPH, PhBuPH and ArP(H)(CH2)3(H)PAr, respectively. A double‐cleavage reaction of Ar2RP may occur in low yield. 2,6‐(Dimethoxyphenyl‐dibutylphosphine gives dibutylphosphine in moderate yield. When compounds with a 2,6‐dimethoxyphenyl moiety are allowed to react with Li/THF, removal of a methyl group leads to novel phosphinophenols. It is concluded that cleavage of alkyl groups R selectively occurs when R° is relatively stabl

ISSN:0165-0513    

DOI:10.1002/recl.19921110402

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractThe effect of pressure on the rates of anaerobic thermal homolytic scission of the CoC bond in alkylcobalamins (RB12, R = adenosyl, methyl and neopentyl) has been determined in different solvents of varying viscosities. Homolytic fission is compared to bond breaking using βH elimination (isopropylcobalamin in ethylene‐glycol + water mixtures) and heterolysis. These two mechanisms are characterized by a volume of activation that is close to zero, whereas homolysis shows a substantial positive value (18.5 cm3ṁ mol−1for AdoB12, 17.0 cm3ṁ mol−1for MeB12and 7.9 cm3ṁ mol−1for neopentylB12, all in ethylene glycol) for this parameter. Consequently, pressure effects can be used, with caution, as mechanistic probes to identify CoC bond fission mechanisms for t

ISSN:0165-0513    

DOI:10.1002/recl.19921110403

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractThe reactions of anisole(1), phenol(2), the alkoxy‐ and alkylphenyl ethers3–11, toluene(12)and theo‐dialkylbenzenes13–15with sulfur trioxide in dichloromethane or trichlorofluoromethane have been studied. Our results have been compared with those obtained with the same substrates upon reaction with SO3in nitromethane and dioxane. We show thatorthosubstitution is enhanced for sterically unhindered phenyl ethers and phenols due to complex formation between SO3and the C(sp2)‐bonded oxygen when dichloromethane is used as solvent instead of nitromethane or dioxane. This is mainly as a result of intramolecular SO3, transfer from the oxygen to theorthocarbon and subsequent conversion of the resulting σ‐complex into theorthos

ISSN:0165-0513    

DOI:10.1002/recl.19921110404

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractRing opening of the octane‐β‐sultones1a‐cby methanol gives the β‐methoxyoctane‐sulfonic acids2a‐cbySN2 substitution at C‐O with inversion of the configuration. Hydrolysis ofcis‐ andtrans‐4,5‐octanesultones1a‐bunder acidic conditions is stereospecific and leads tothreo‐ [(RR,SS)‐4u] anderythro‐5‐hydroxy‐4‐octanesulfonic acid [(RS,SR)‐4u], respectively, by a similarSN2 reaction on the carbon of the CO bond. Hydrolysis of 4,5‐octanesultones1a‐bwith base proceeds by attack at the sulfur atom of the β‐sultone ring to provide 5‐hydroxy‐4‐octanesulfonates(4v)with retention. Reaction of carbyl sulfates5a‐bwith methanol gives the methyl esters of 5‐hydroxy‐4‐octanesulfonic acid7a‐bin a stereospecific way with retention of co

ISSN:0165-0513    

DOI:10.1002/recl.19921110405

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractAlkylation of the α‐lithio anion of 2,3,4,5,6‐penta‐O‐benzyl‐myo‐inositol 1‐(methanesulfonate) with 1,2‐O‐isopropylidene‐sn‐glycerol 3‐(trifluoromethanesulfonate) gave, after removal of the acetonide function followed by palmitoylation and finally hydrogenolysis of the benzyl protecting groups, the racemic phosphatidylinositol analog3. The methyleneoxy‐containing inositol phospholipid4was prepared by iodonium‐ion‐assisted condensation of 1,2‐O‐isopropylidene‐3‐(methylthiomethyl)‐sn‐glycerol with 2,3,4,5,6‐penta‐O‐benzyl‐myo‐inosi

ISSN:0165-0513    

DOI:10.1002/recl.19921110406

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19921110407

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19921110409

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY