摘要:

AbstractSingle crystals of theN,N,N′,N′‐tetramethylethylenediamine (TMEDA) complex6of the title compound have been isolated. Compound6decomposes in the crystalline state above −20°. From the bond lengths and angles obtained by X‐ray crystal‐structure analysis (data collected at −70°), compound6is best described as a (E)‐1‐(tert‐butylthio)‐1‐lithio‐2‐butene with the double bond acting as an additional ligand on lithium (unsymmetrical allylic group). The S‐atom is in acisoidarrangement in a common plane with the four C‐atoms of the butenyl system. Thet‐Bu group and the Li‐atom are located above and below this plane. The structure is discussed with respect to the reactivity of6(α/γ reactivity). The gross structure is reproduced surprisingly well by anab initioSCF MO calculation of the model lithiopropene‐1‐thiol7(HS instead oft‐BuS, CH2instead of CHCH3, no solvation of Li). The prominent difference is the symmetry of th

ISSN:0018-019X    

DOI:10.1002/hlca.19880710202

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractThe solvolysis rates and products of several 1‐substituted 2exo‐ and 2‐endo‐norbornylp‐toluenesulfonates7and8, respectively, have been determined. Hydrolyses of these epimeric tosylates yielded rearranged products in varying amounts, except when the substituent was COOCH3or CN. The logarithms of the rate constants (logk) for theendo‐series8correlated linearly with the corresponding inductive constants σ 1qwith a reaction constant ρIof −1.24. On the other hand, logkvalues for theexo‐series7appear to fit two regression lines, the first line (ρI= −1.90) defined by the tosylates that ionize, with rearrangement, to the tertiary cations11, the second (ρI= −1.86) by the tosylates7(R = H, COOCH3, and CN) that ionize to an asymmetrically bridged secondary cation19. These results confirm the unique participation of C(6) with a ρIof −2.00 in the ionization

ISSN:0018-019X    

DOI:10.1002/hlca.19880710203

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractThe isoproterenol analogues4aand4b, synthesized as mixtures of Diastereoisomers, were shown to possess very potent β‐adrenoceptor agonistic activity. Therefore, the four possible diastereoisomers of4ahave been synthesized and tested for inotropic activity. The (6R, 2′R)‐diastereoisomer turned out to be the most interesting one. Consequently, also (6R,2′R)‐4bhas been prepared and tested. For the diastereoselective synthesis, three variants have been elaborated: (i) coupling of epoxides12with amines27(Scheme 6); (ii) coupling of the activated glycol17with the amine22(Scheme 8); (iii) diastereoselective hydrogenation of the amino ketone31(Scheme 7). Both (6R,2′R)‐4aand (6R,2′R)‐4bshow long lasting positive inotropic activity after intravenous as well as oral administration and are at least three times as potent asrac‐isoproterenol. In the anesthetized dog, a good separation of positive inotropic and positive chronotropic effects is observed. In conscious dogs, however, heart rate and contractile force increase to the same extent (possibly due to

ISSN:0018-019X    

DOI:10.1002/hlca.19880710204

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

Note on the Synthesis of an Optically Active ACE Inhibitor with Amino‐oxo‐benzazepine‐1‐alkanoic‐Acid Structure by Means of an Enantioconvergent Crystallization‐Based ResolutionAn enantioselective synthesis of the potent angiotensin‐converting enzyme inhibitor (1′S,3S)‐3‐[(1′‐(ethoxy‐carbonyl)‐3′‐phenylpropyl)amino]‐2,3,4,5‐tetrahydro‐2‐oxo‐1H‐1‐benzazepine‐1‐acetic acid hydrochloride (3) is described which user a crystallization‐based resolution of a racemic amino intermediate with

ISSN:0018-019X    

DOI:10.1002/hlca.19880710205

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

Synthesis of Natural, Halogenated IndolesviaHetero‐CopeRearrangement of VinylN‐PhenylhydroxamatesAn efficient method for the synthesis of natural 4‐chloro‐6‐methoxyindole (the promutagen from fava beans) and of the two 4,6‐ dibromo‐ and 3,4,6‐tribromoindoles (produced by acorn worms,Enteropneusta) is presented. The key step is a hetero‐Coperearrangement of the intermediateN‐phenyl‐O‐vinylhy

ISSN:0018-019X    

DOI:10.1002/hlca.19880710206

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

New Flavonoid Glycosides fromPaeonia tenuifoliaL.Two novel flavonoid glycosides have been isolated from the stamens ofPaeonia tenuifolia, sexangularetin‐3‐O‐yl β‐D‐sophoroside (1) and limocitrin‐3‐O‐yl β‐D‐sophoroside (3). Their structures have been elucidated by spectroscopic means, mainly desorption chemical ionisation mass spectrometry and ID and 2D high‐resolution1H‐NMR spectroscopy of

ISSN:0018-019X    

DOI:10.1002/hlca.19880710207

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractThe protected serine aldehyde10was converted to the crystallineN‐Boc‐protected sphingosines6–9by a three‐step reaction sequence. Compound10was transformed with high diastereoselectivity (95%) either to theerythro‐ orthreo‐alkynols,17and18, respectively. Theerythro‐isomer17is formed by the addition to10of lithium pentadecyne16in THF/HMPT at −78°, whereas the correspondingthreo‐isomer18is produced in the presence of ZnBr2in Et2O. Deprotection of the acetal moiety afforded 1,3‐diols19and20. These diols were selectively reduced with Red‐Al to the(E)‐sphingosines6and8, or the(Z)‐isomers7and9by partial hydrogenation overLindlar'scatalyst. Cleavage of theN‐Boc group and further transformation to ceramides were readily achieved as demonstarted by the conversion of6toN‐octad

ISSN:0018-019X    

DOI:10.1002/hlca.19880710208

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

Polycyclopentanes as Steroid AnalogaThe synthesis of linearly annellated pentaquinanes from a readily available triquinane is reported.

ISSN:0018-019X    

DOI:10.1002/hlca.19880710209

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractA new Si‐inducedVilsmeier‐type formylation of F‐containing organozinc reagents is described. This two‐step processviathe isolable intermediate10seems to be quite general for the synthesis of anhydrous polyhalogenated al

ISSN:0018-019X    

DOI:10.1002/hlca.19880710210

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractThe photolysis of 7,8‐dihydro‐4‐hydroxy‐β‐ionone (6) was investigated together with its acetate and isopropyl ether7and8, respectively. Irradiation (λ>245 nm) of6in MeCN or i‐PrOH at temperatures between 25° and −65° leads to the tricyclic ethers9,10and13A+B, and to the spirocyclic ethers11and12, which are all known types of photoproducts, previously obtained on photolysis of 7,8‐dihydro‐β‐ionone (1). The same types of products are obtained on irradiation of the acetate7and the isopropyl ether8. On the other hand, irradiation of the hydroxy compound6in MeCN or i‐PrOH at temperatures between −35° and −65° leads to the new tricyclic tertiary alcohols14and15as the major products. Their formation involves an intramolecular trapping of a carbocation by the neighbouring OH group, thus, supporting the previously proposed mechanism of the transformation1→5.For structure proof, the tricyclic alcohol14and the pheny1 carbamate42, derived from9

ISSN:0018-019X    

DOI:10.1002/hlca.19880710211

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY