摘要:

AbstractOxidation of patchouli alcohol (1) using the ‘Gif system’ afforded as major isolated products three new ketonic derivatives16–18. The structures of these compounds were established by spectral techniques including 2D‐NMR. Ketones16–18display interesting organoleptic p

ISSN:0018-019X    

DOI:10.1002/hlca.19870700202

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractGloeosporone, the germination self‐inhibitor from the fungusColletotrichum gloeosporioidesf.sp.jussiaea, is shown by spectroscopic data and X‐ray analysis to have the constitution and relative configuration as shown inFormula2(either (1S,6R,12R)‐1‐hydroxy‐6‐pentyl‐5,15‐dioxabicyclo[10.2.1]pentadecan‐4,13‐dione or its enantiomer), rather than the previously ass

ISSN:0018-019X    

DOI:10.1002/hlca.19870700203

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

Electrochemical Oxidation of (S)‐Malic‐Acid Derivatives: a Route to Enantiomerically Pure Alkylmalonaldehydic EstersThe 3,3‐dialkymalic‐acid diesters, prepared by the previously described diastereoselective alkylations through dilithium alkoxide enolates, are saponified to the monoesters containing a free α‐hydroxycarboxylic‐acid moiety(Scheme 3). The monoesters are subjected to electrochemical oxidative decarboxylation inMeOH. If the intermediate monoacids are purified, the malonaldehydic esters (2‐formy1‐2‐alkylcaroxylates) Obtained by this procedure are enantiomerically pure; they have the same structural features,i.e.two enantiotopic functionalized branches on the (persubstituted) stereogenic center, as the well known 3‐hydroxy‐2‐methylpropanoic acid (‘Rocheacid’) which was employed frequently as a starting material for the preparation of either enantiomer

ISSN:0018-019X    

DOI:10.1002/hlca.19870700204

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractThe PE spectroscopic data for a series of [2.2]paracyclophanes with olefinic and/or aromatic bridges, and of a few related molecules are reported, together with tentative assignments based on simple MO models.

ISSN:0018-019X    

DOI:10.1002/hlca.19870700205

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

Ring Enlargement by Lactonization of Methylated 1‐(3′‐Hydroxypropy1)‐2‐oxocyclododecane‐1‐carbonitrilesThe title compounds were prepared byMichaelreaction of 2‐oxocyclododecane‐1‐carbonitrile (1) and acrylaldehyde and its derivatives followed by NaBH4reduction or methylation of the aldehyde group with [(CH3)2Ti(i‐PrO)2] (Scheme 1). In all cases, the ring enlargement was performed with Bu4NF/THF to give different methylated derivatives of 12‐cyano‐15‐pentadecanolide (13) in 95–99% yield. The Yields of the rearrangement products are not dependent on the positions and numbers of the CH3groups in the side chain of3. The lactonization reaction is of u

ISSN:0018-019X    

DOI:10.1002/hlca.19870700206

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

Synthesis of Methyl ω‐(5‐Oxo‐1‐cyclopentenyl)alkanoates Starting from 2‐NitrocycloalkanonesA convenient synthesis of methyl ω‐(5‐oxo‐1‐cyclopentenyl)alkanoates1is described. 2‐Nitrocycloalkanones2are converted to 2‐(3,3‐dimethoxypropy1)‐2‐nitrocycloalkanones4. Treatment of4with MeOH/MeONa led to the ring‐opened nitronates5which underwent aNefreaction to form the corresponding oxo derivatives6. Partial hydrolysis of followed by base‐catalyzed aldol reaction gave th

ISSN:0018-019X    

DOI:10.1002/hlca.19870700207

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractThe [2 + 2]‐cycloaddition of dichloroketene (preparedin situfrom CCl3COCl and Zn(Cu)) with three alkynes1a–cto form 2,3‐dimethyl‐(2a), 2,3‐diethyl‐(2b) and 3‐butyl‐4,4‐dichlorocyclobut‐2‐enone (2c) proceeds rapidly in the absence of POCl3. The primary products2a–crearrangein situto the 2,4‐dichlorocyclobut‐2‐enones3a–cunder the influence of ZnCL2produced during the reaction. ZnCl2converts both2aand3ainto a 4:6 equilibrium mixture of the two; this isomerization does not occur with LiCl. The Cl‐atoms of both2a,band3a,band of2cmay reductively be removed with Zn(Cu) in AcOH/pyridine to afford the alkylcyclobutenones4a‐c. Without pyridine, this reduction givesca.1:1 mixtures of the double‐bond isomers4and5in low yields. The cyclobutenones2cand4cmay be deuterated by CD3COOD in the presence of pyridine.D‐Atom is introduced into2cat C(4) and at C(γ), and into4cat C(2) and C(4). A mechanism for this deuteration is considered, which does not involve a cyclobutadienolate7, but rather a cyclobutenolate of type8. The reductions of2and3to4might also pas

ISSN:0018-019X    

DOI:10.1002/hlca.19870700208

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

3‐(Dimethylamino)‐2,2‐dimethyl‐2H,‐azirine as an α‐Aminoisobutyric‐Acid (Aib) Equivalent: Cyclic DepsipeptidesviaDirect Amid CyclizationIn MeCN at room temperature, 3‐(dimethylamino)‐2,2‐dimethyl‐2H‐azirine (1) and α‐hydroxycarboxylic acids react to give diamides of type8(Scheme 3). Selective cleavage of the terminalN,N‐dimethylcarboxamide group in MeCN/H2O leads to the corresponding carboxylic acids13(Scheme 4). In toluene/PhSH, phenyl thioesters of type11are formed (see alsoScheme 5). Starting with diamides8, the formation of morpholin‐2,5‐ diones10has been achieved either by direct amide cyclizationviaintermediate 1,3‐oxazol‐5(4H)‐ones9orviabase‐catalyzed cyclization of the phenyl thioesters11(Scheme 3). Reaction of carboxylic acids with1, followed by selective amide hydrolysis, has been used for the construction of peptides from α‐hydroxy carboxylic acids and repetitive α‐aminoisobutyric‐acid (Aib) units (Scheme 4). Cyclization of14a, 17a, and20awith HCI in toluene at 100° gave the 9‐, 12‐, and 15‐

ISSN:0018-019X    

DOI:10.1002/hlca.19870700209

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractPropargyl‐alkyl biradical12generated by photodecarbonylation of title ketone3undergoes ring closure to cyclobutane7and to vinyl carbene13, this latter intermediate rearranging to the 5‐ethylidenecyclopentenes8aan

ISSN:0018-019X    

DOI:10.1002/hlca.19870700210

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

Novel Triterpene Lactones ofHelenium autumnaleL.Three novel triterpene lactones1–3could be detected by investigating a pentane extraxt of theHelenium autumnaleL. (Asteraceae) roots. The structures are especially elucidated by1H‐ and13C‐NMR spectroscopy. The lactones1‐3formally representDiels‐Alderproducts of a reaction between a sesquiterpene lactone and an α,β‐unsaturated sequiter

ISSN:0018-019X    

DOI:10.1002/hlca.19870700211

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY