摘要:

AbstractAddition of dialkyl phosphites to the nitrone6, formedin situfrom the oxime5and formaldehyde gave the hydroxylamines7(86%) and8(88%), which reacted withp‐benzoquinone in the presence of ethyleneviatheC‐dialkoxyphosphonoylnitrones9and10to yield the cycloaddition products11–14(80–85%) with a diastereoselectivity of about 50%. The cycloaddition products were transformed into the monoisopropylidene derivatives15–18and the diacetates19–22. Comparison of the NMR spectra and the specific rotations of the compounds19–22with those of the corresponding α‐ammo‐acid derivatives23–26of known configuration indicated preferential formation of theL‐isomers. The cycloaddition products were transformed in good yield into theL‐α‐aminophos

ISSN:0018-019X    

DOI:10.1002/hlca.19820650702

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY

摘要:

AbstractSelected oligo‐L‐lysine carriers and a poly‐L‐lysine were penicilloylated with benzylpenicillin. The resulting conjugates2–6were studied by IR. absorption in the solid state and circular dichroism measurements in solution. The IR. data demonstrate the lack of β‐structure formation even in medium‐sized peptides where such structures might be expected on the basis of previous studies on differently substituted oligo‐L‐lysines. Considerable proportions of right‐handed α ‐helical conformation are exhibited by the icosa‐L‐lysine and poly‐L‐lysine conjugates5and6in water and 2,2,2‐trifluoroethanol. Difficulties in obtaining fully penicilloylated conjugates are not related to the extent of α‐heli

ISSN:0018-019X    

DOI:10.1002/hlca.19820650703

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY

摘要:

Abstract(2‐Butenyl)‐, (4‐methyl‐2‐pentenyl)‐, and (2‐heptenyl)triphenoxytitanium (2a–c) add to dialkyl, alkyl aryl‐, and alkinyl aryl ketones to give high yields of tertiary homoallylic alcohols (5–12), which are diastereomerically enriched up to 98%. Configurational assignment by degradation of two of the products to olefins15and18‐ through β‐hydroxy acids13and16and β‐lactones14and17‐ leads to the proposal of a general mechanism and of a specification of the relative topicitylkof the process (Scheme 5). The allylic Ti‐compounds2can serve as d2‐reagents (see the d2‐synth

ISSN:0018-019X    

DOI:10.1002/hlca.19820650704

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY

摘要:

AbstractThe photoelectron (PE.) spectrum of the title compound has been assigned by comparison with the PE. spectrum of cubane (2), aided byab initioSTO‐3G calculations using localized molecular orbitals. On the basis of the information available to date, the most satisfactory orbital sequence,Koopmanstheorem implied, is, in descending order of energy: band system : (2e″2, 3e′22e″1, 3e′1); band system : 3a′1(2e′2, 2a″2); band : 2e′1.(Sequence of orbitals in paren

ISSN:0018-019X    

DOI:10.1002/hlca.19820650705

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY

摘要:

Ring Closure in Quinonylmethane Dyes On the Reactivity of the Cyciohexyl Moiety in 2‐Chloro‐3‐[(1‐cyclohexyl‐6‐fluoro‐3‐methyl‐1H‐quinoxalin‐2‐ylidene)niethyl]‐1,4‐naphthoquinoncThe reactive title compound (1a,X=F,R1= C6H11,R2=Cl) was obtained from the reaction of 1‐cyclohexyl‐6‐fluoro‐2,3‐dimethylquinoxalinium perchlorate with 2,3‐dichloro‐1,4‐naphthoquinone. Upon treatment with pyridine and acetic acid in acetone and separation of the desired naphthophenazinone2a, an unexpected azepinoquinoxaline4awas isolated. The structure of4awas determined by its mass and 360‐MHz‐1H‐NMR.

ISSN:0018-019X    

DOI:10.1002/hlca.19820650706

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY

摘要:

AbstractAtom pair potentials are obtained fromab initioSCF‐LCAO‐MO calculations for model complexes of Mg2+and Ca2+withN,N‐dimethylacetamide, and malonamide. The SCF‐LCAO‐MO interaction energies for 271 complexes of Mg2+and 271 complexes of Ca2+with these amides were fitted with a simple analytical potential by a least‐square procedure. Interaction energies and optimal ion locations obtained by pair‐potential calculations are compared with values obtained byab initiocalculations for some related amides. The application of the atom pair potentials to the structure of the Mg2+‐complex [MgCl2(C3H7ON)6] ofN‐ethylaceta

ISSN:0018-019X    

DOI:10.1002/hlca.19820650707

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY

摘要:

AbstractA systematic study of vibronic excitation in benzeneviaforward electron scattering was carried out using a novel type of a trochoidal electron spectrometer. Energy‐loss spectra in the energy range 1.0–9.5 eV, with residual energies 0.03–20 eV as well as excitation functions for individual vibrational levels of some of the triplet and singlet states are presented and discussed. Following observations were made. (1) A new s‐typeRydbergseries with quantum defect δ = 0.86. (2) Additional information on the complex 6–6.5 eV band. (3) A new core excited shape resonance at 6.5 eV. (4) A narrowFeshbachresonance at 5.87 eV, The new spectrometer is suggested as a tool for routine study of forbidden transitions and negative ion states in organic

ISSN:0018-019X    

DOI:10.1002/hlca.19820650708

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY

摘要:

Abstract4,4‐Dimethyl‐dihydro‐2,3‐furanedione (4), an intermediate in the synthesis of (+)‐D‐pantothenic acid, is obtained in good yield from readily available substances such as isopropyl chloride, diethyl oxalate and formaldehyde, without oxidative

ISSN:0018-019X    

DOI:10.1002/hlca.19820650709

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY

摘要:

Synthesis of some 1,2‐DihalogenonorbornanesThe synthesis of 1,2exo‐Dibromo‐norbornane as well as the preparation of the configurational isomers of 2‐bromo‐1‐iodo‐ and 2‐chloro‐1‐iodo‐nor

ISSN:0018-019X    

DOI:10.1002/hlca.19820650710

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY

摘要:

Abstract1,2exo‐Diiodo‐norbornane (4) was prepared from norcamphor hydrazone by oxidative iodination and subsequent rearrangement of the 2,2‐diiodo‐bicyclo [2.2.1]heptane (2). The stable α‐iodohydrazone11was obtained from 1‐iodo‐bicyclo[2.2.1]heptan‐2‐one (10), which itself was prepared from 1‐iodo‐norbornene (5). Subsequent treatment of11with iodine lead to 1,2,2‐triiodo‐norbornane (12) and l,2‐diiodo‐norborn‐2‐ene (13). 1,2endo‐Diiodo‐norbornane (14) was obtained by stereoselective reduction of12with tribtityltinh

ISSN:0018-019X    

DOI:10.1002/hlca.19820650711

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY