摘要:

AbstractUsing the method ofGuibeet al. we were able to selectively introduce an allyl group at the 2‐position in methyl‐4,6‐O‐(tetraisopropyldisiloxane‐1,3‐diyl)‐α‐D‐glucopyranoside and benzyl‐4,6‐O‐(tetraisopropyldisiloxane‐1,3‐diyl)‐β‐D‐glucopyranoside. The dynamic properties of the tetraisopropyldisiloxane‐1,3‐diyl protective group gave us access to a glucose derivative which carried a 1‐propenyl group at the 2‐position, an allyl group at the 6‐position and a tetraisopropyldisiloxane‐1,3‐diyl at the 3,4‐position together with a glucose derivative protected with an allyl, an acetyl and a 3‐hydroxytetraisopropyldi

ISSN:0165-0513    

DOI:10.1002/recl.19831021201

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractThe synthesis of a variety of substituted indenethioneS‐oxides (all α,β‐unsaturated sulfines) is described. Essentially these sulfines are prepared by the reaction of α‐silyl carbanions with an excess of sulfur dioxide (modifiedPetersonreaction). The requisite α‐silyl carbanions are generated by two different routes,i.e.by α‐deprotonation of trimethylsilyl‐substituted indenes and by nucleophilic δ‐addition of alkyllithium compounds to dienesilanes. In all cases, the sulfines prepared were converted into cycloadducts by reaction with 2,3‐d

ISSN:0165-0513    

DOI:10.1002/recl.19831021202

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractTreatment of a solution of 3‐nitro‐2‐X‐1,5‐naphthyridines (X = H, OC2H5, Cl, NH2, OH) in liquid ammonia with potassium permanganate gives the corresponding 4‐amino‐3‐nitro‐2‐X‐1,5‐naphthyridines in moderate to good yields.From1H NMR spectroscopy, good evidence has been obtained for the intermediacy of 4‐amino‐1,4‐dihydro‐3‐nitro‐2‐X‐1,5‐na

ISSN:0165-0513    

DOI:10.1002/recl.19831021203

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractThe solvent dependence of the enthalpies and entropies of activation for the title reactions in water‐richt‐BuOH‐H2O responds to the hydrophobicity of the subs

ISSN:0165-0513    

DOI:10.1002/recl.19831021204

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractThe irradiation of2in acetonitrile or methanol with λ 254 nm yields the tetronic acid derivative3. The (thermal) BF3‐catalyzed rearrangement of2yields the same tetronic acid derivative. The structure of the tetronic acid3has been determined by means of X‐ray analysis; it forms monoclinic crystals with cell constantsa= 10.868,b= 8.320,c= 20.936 Å and β = 90.65°. The space group isP21/n; in the unit cell there are eight molecules which exhibitintermolecular hydrogen

ISSN:0165-0513    

DOI:10.1002/recl.19831021205

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY

摘要:

Abstractα‐Alkylation of esters,e.g.AcO‐iPr → AcO‐tBu, results in a large rate increase for β‐elimination of acetic acid, indicating that in the transition state Cαis positively charged. Replacement of α‐H by electron‐attracting groups Z, such as COOMe,alsoenhances the rate of formation of alkene. Neither differences in product stability nor steric acceleration appear to play a significant role. A major factor is dipolar destabilization of starting compounds containing two electronegative groups, such as AcOCMe2Z compared with AcO‐tBu. The free energies of the transition states are found to parallel those of the fully ionized species, AcO(‐)+ R(+).At elevated temperatures, esters such as AcOCMe(CN)Ph will give rise to O‐C bond homolysis rather than to molecular eli

ISSN:0165-0513    

DOI:10.1002/recl.19831021206

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractPhosphorylation of 3′‐O‐levulinoylthymidine*** using 2‐chlorophenyl bis‐O‐(1‐benzo‐triazolyl) phosphate, followed by addition of 1‐hexadecanol, afforded in high yield a fully protected triester derivative of thymidine.Similarly, phosphorylation of 1,2‐di‐O‐palmitoyl‐sn‐glycerol with the same reagent and subsequent addition of the above thymidine derivative gave a triester derivative of thymidine in excellent yield. Both triester derivatives were efficiently converted into the corresponding liponucleotides by the removal of the 2‐chlorophenyl and

ISSN:0165-0513    

DOI:10.1002/recl.19831021207

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractThe synthesis of a teichoic acid fragment (i.e.compound8e), containing three 3‐O–(β‐glucopyranosyl)‐sn‐glycerol residues connected via two phosphodiester linkages, is described. The assemblage of the teichoic acid fragment was effected using a modified phosphotriester approach based on the use of 1‐hydroxybenzotriazole‐activated phosphorylating agents (i.e.phosphorylating agents5cand6c). Three suitably protected building blocks were prepared:i.e.,2b,3cand4b. Special attention was paid to the preparation of the middle unit3cwhich contains a stable phosphodiester anilidate to avoid intramolecular reaction of the free hydroxyl function on phosphorus. Compound2bwas condensed with derivative3cto give fragment7a. The aniline group could be removed from dimer7ato give7b, which was then condensed with monomer4bto give the fully protected teichoic acid fragment8a. Stepwise removal of the protecting group of8aafforded the teichoic a

ISSN:0165-0513    

DOI:10.1002/recl.19831021208

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractThe decomposition of ethyl diazoacetate catalyzed by Cu(II)‐exchanged zeolite NaX, has been studied. Catalytic activity required at least 25% sodium exchange of the zeolite. From 25% exchange to higher exchange levels the decomposition rate increased linearly with the copper introduced into the zeolite. With cyclohexane as the solvent, the (ethoxycarbonyl)carbene formed was found to yield dimers, diethyl maleate and diethyl fumarate, and also compounds resulting from reaction with the solvent or with residual water present in the zeolite. Reduction of Cu(II) to Cu(I) increased the activity of the catalysts. The degree of hydration of the zeolite had a large effect on the activity of the catalyst and on the selectivity of the reaction. Complexation of the Cu(II) ions with NH3or 1,2‐propanediamine reduced the activity of the zeolite drastically. Zeolite NaCuX showed no induction time in contrast to several copper salts tes

ISSN:0165-0513    

DOI:10.1002/recl.19831021209

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractCyclopropane C‐H separated from an alkoxy group by one, two or three carbon atoms can be lithiated if intramolecular coordination between Li and OR is possible in the reaction produc

ISSN:0165-0513    

DOI:10.1002/recl.19831021210

出版商:WILEY‐VCH Verlag    

年代:1983

数据来源: WILEY