Helvetica Chimica Acta

doi: 10.1002/hlca.19880710101pmid: N/A

Eberle, Martin; Egli, Martin; Seebach, Dieter

doi: 10.1002/hlca.19880710102pmid: N/A

Enantioselective Saponification of Diacetates of 2‐Nitro‐1,3‐propanediols by Pig‐Liver Esterase and Preparation of Enantiomerically Pure Derivatives of 2‐Nitro‐allylic Alcohols (Chiral Multiple‐Coupling Reagents)

Märki‐Fischer, Edith; Eugster, Conrad Hans

doi: 10.1002/hlca.19880710103pmid: N/A

Stereoisomeric Sinensiaxanthins and Sinensiachromes: Separation and Absolute Configuration

de Almeida, Ligia Bicudo; De Vuono Camargo Penteado, Marilene; Britton, George; Uebelhart, Peter; Acemoglu, Murat; Eugster, Conrad Hans

doi: 10.1002/hlca.19880710104pmid: N/A

The 5,6:5′,6′‐diepoxy‐5,6:5′,6;‐tetrahydro‐β,β‐carotene, isolated from tubers of a white‐fleshed variety of sweet potato (Ipomoea batatas LAM.) has been assigned the (5R,6S,5′R,6′S)‐chirality on the basis of its HPLC, UV/VIS, and CD data.

Gunzenhauser, Sigmund; Balli, Heinz

doi: 10.1002/hlca.19880710105pmid: N/A

Halochromic Molecules. Synthesis and Acidobasic Properties of Substituted Heteroarenoquinazolines

Rösslein, Lukas; Tamm, Christoph

doi: 10.1002/hlca.19880710106pmid: N/A

The ‘syn’‐1,3‐diols 3,4 and 5 with a C7, C6, and C5 chain, respectively, were synthesized from methyl hydrogen 3‐hydroxyglutarate (2; Schemes 1 and 2). The latter is available in (R)‐ and (S)‐configuration. Octyl (3R)‐4‐chloro‐3‐hydroxybutanoate (17) is an alternative starting material for the preparation of 5 (Scheme 3.) The epoxide 20, derived from 5 in a one‐pot reaction, is a versatile synthon, which selectively reacts with a great number of nucleophiles (Scheme 4).

Guerriero, Antonio; D'Ambrosio, Michele; Pietra, Francesco; Cuomo, Vincenzo; Vanzanella, Fortunato

doi: 10.1002/hlca.19880710107pmid: N/A

The novel metabolite dendryphiellin A ( = (+)‐(1R,2S,8aR)‐ 1,2,6,7,8,8a‐hexahydro‐7‐hydroxy‐1,8a‐dimethyl‐6‐oxonaphthalen‐2‐yl (6R*, 2E,4E)‐8‐hydroxy‐6‐methylocta‐2,4‐dienoate; (+)‐1) is isolated from cultures of the marine deuteromycete Dendryphiella salina. There is no precedent in fungi for trinor‐eremophilanes or for branched C9 carboxylic acids, the two classes of compounds constituting (+)‐1. The structure is secured by NMR spectroscopy and hydrolysis of (+)‐1 to give the side‐chain moiety ((6R*,2E,4E)‐8‐hydroxy‐6‐methylocta‐2,4‐dienoic acid (2)) intact, whilst the trinor‐ermophilane moiety is decomposed. The absolute configuration at the trinor‐eremophilane moiety is established from exciton coupling between the dienone and the diene‐ester functions.

Guella, Graziano; Pietra, Francesco

doi: 10.1002/hlca.19880710108pmid: N/A

Two novel pregnatrienolones isolated in very small amounts from the North‐East‐Atlantic demosponge Axinella agnata (Tetractinomorpha, Axinellida) are unique in having C(2)C(3) (or C(3)C(4)), C(7)C(8), and C(16)C(17) bonds and a 12β‐OH group which, being strongly H‐bonded to a 20‐keto group, resists acylation. 1H‐ and 13C‐NMR spectroscopy of the steroids and of products of their selective epoxidation or reduction allow us to propose the structures (+)‐12β‐hydroxy‐5α‐pregna‐2,7,16‐trien‐20‐one ( = agnatasterone A, (+)‐1), and (+)‐12β‐hydroxy‐5α‐pregna‐3,7,16‐trien‐20‐one ( = agnatasterone B. (+)‐5), for the two steroids with minimal recourse to model compounds.

Gunzinger, Jan; Hostettmann, Kurt; Msonthi, Jerome D.

doi: 10.1002/hlca.19880710109pmid: N/A

Four new pterocarpinoids, sphenostylin A, B, C, and D (1–4), have been isolated from the CHCl3 extract of the root bark of Dolichos marginata ssp. erecta (Leguminosae) by preparative liquid chromatography. The structures have been established by spectroscopic methods (UV, 1H‐NMR, 13C‐NMR, EI‐MS, DCI‐MS, CD) and chemical transformations. The isolated compounds showed weak antifungal activity against Cladosporium cucumerinum.

Nagarajan, Kuppuswamy; Rao, Vunnam R.; Shah, Rashmi K.; Shenoy, Sharada J.; Fritz, Hans; Richter, Wilhelm J.; Muller, Dieter

doi: 10.1002/hlca.19880710110pmid: N/A

Homophthalic acid (1) undergoes reaction with 1,2‐, 1,3‐, and 1,4‐diamines to give condensed 1(2H)‐isoquinolinones like 2, 4, 13, and 25, which exhibit marked enamine character. These are attacked by electrophiles at the N or C terminus. Some notable reactions of imidazoisoquinolone 2 are those with maleic and acrylic acids to form the tetracycles 48 and 51, respectively. With propiolic acid, 5 underwent an interesting reaction to form the benzimidazonaphthyridine 53. An equally interesting behaviour was elicited from 2 in its reaction with formaldehyde, when in addition to the expected methylene‐bridged molecule 59, the novel spiro derivative 60 was formed by the dimerisation of a presumed azadiene intermediate 63.