共查询到20条相似文献,搜索用时 9 毫秒
1.
Karl Schaffner-Sabba Beat W. Müller Riccardo Scartazzini Hansuli Wehrli 《Helvetica chimica acta》1980,63(2):321-326
A Simple Route to 3-Amino-nocardicinic Acid Starting from nocardicin A ( 1 ), a novel and efficient procedure for the preparation of 3-amino-nocardicinic acid ( 4 ) and its protected derivatives 6 and 8–11 is described. 相似文献
2.
Riccardo Scartazzini 《Helvetica chimica acta》1977,60(5):1510-1521
New β-lactam antibiotics. Functionalisation of 3-hydroxy-3-cephem-4-carboxylic esters through the Wittig reaction The 3-hydroxy-ceph-3-em-esters 1a, b reacted smoothly with stabilized phosphor-ylids to give a series of derivatives which were converted into the microbiologically active acids 14a, c, 15c and 20 by known procedures. The synthesis of the amides 23, 24, 26 and of the ester 28 from the 3-carboxymethyl-derivative 19 is also reported. 相似文献
3.
3-Hydroxy-ceph-3-em-esters 5 a – c , versatile intermediates for the preparation of new β-lactam antibiotics, were obtained by ozonolysis of the corresponding 3-methylidene-esters 3 a – c . Reduction and elimination gave the 3-unsubstituted ester 13 ; derivatives 16 a – c and 20 – 22 resulted from O-alkylation. The 3-methoxy-esters 16 a – c were converted into the corresponding acids 23 a – d . Several other transformations of the β-ketoester system are described. 相似文献
4.
W. K. J. Schoor 《Fresenius' Journal of Analytical Chemistry》1885,24(1):102
Ohne Zusammenfassung 相似文献
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The syntheses of 4-methyl-, 4-ethyl-, 4-isopropyl-and 4-t-butylquinuclidine are described. The key step in the synthesis of 4-t-butylquinuclidine involves a modified Koch-Haaf reaction leading from a δ-amino-tert. alcohol to an ester of the homologous acid. 相似文献
8.
Benzhydrylic esters of 3-unsubstituted cephem-4-carboxylic acids of types 9 and 10 (Scheme 2) are prepared by decarbonylation of esters of 3-formylcephem compounds of type 2 with tris-triphenylphosphine-rhodium chloride. The preparation of the starting materials 2 and 5 , as well as of the nucleus 13 is described. 相似文献
9.
The treatment of drevogenin P with isovaleryl chloride in pyridine gave an amorphous 3,12-di-O-isovaleryl-drevogenin P ( 4 ), which, on energetic acetylation, was converted into 3-O-isovaleryl-drevogenin A ( 5 ). This could be isolated in crystalline form and was converted through mild alkaline hydrolysis into drevogenin A. Hence drevogenin A could be classified as 11-O-acetyl-12-O-isovaleryl-drevogenin P. Indirectly, the structure of drevogenin B could be deduced to be most probably that of 11α-mono-O-acetyl-drevogenin P. Some details of the earlier given structures [1] are corrected here. Drevogenin D has an 11α-hydroxyl group. 相似文献
10.
Hirundigenin can easily be converted into anhydrohirundigenin by thermal dehydration. Both substances are stable to alkali but unstable under acid conditions. Dehydrogenation of anhydrohirundigenin, using selenium at 310°, gave a mixture of 2-methylphenanthrene ( 29 ), 1, 2-dimethyl-phenanthro [1,2-b] furan ( 30 ) and 1-ethyl-2-methyl-phenanthro [1,2-b] furan ( 32 ), all of which could be isolated in crystalline form. The last two substances are new and their structures were confirmed by synthesis. Through these results, as well as by further reactions and spectra, it could be shown that hirundigenin and anhydrohirundigenin are 16-methyl-15-oxapregnane derivatives, further, that they have two epoxide rings and that they probably have the structures 7 and 11. These structures were proved by O. Kennard et. al. through X-ray studies of p-bromobenzoyl-anhydrohirundigenin ( 13 ). As far as we know, 15-oxasteroids had not yet been found in nature. 相似文献
11.
Mansonin is the 2,3-di-O-methyl-6-deoxy-β-D-glucopyranoside of strophanthidin, and strophothevoside the corresponding 3-O-methyl-6-deoxy-β-D-glucopyranoside. 相似文献
12.
The antibiotic roridin D (C29H38O9), a companion of roridin A, yields on base catalysed hydrolysis verrucarol ( 3 ) and the hitherto unknown 2, 3-epoxy-2-anhydrororidinic acid ( 4 ) (C14H18O7). Roridin D is a macrocyclic diester to which structure 1 is assigned. In roridin D an epoxy group replaces the hydroxyl group of roridin A. 相似文献
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Ursula Baumann 《Fresenius' Journal of Analytical Chemistry》1963,193(3):218
Ohne Zusammenfassung 相似文献
16.
E. Venkata Rao D. Venkata Rao S. K. Pavanaram J. Von Euw T. Reichstein 《Helvetica chimica acta》1971,54(7):1960-1968
Corchoroside B has the empirical formula C29H42O8 and was found to be a L -rhammoside of canarigenin ( 5 ), most probably the α, L-rhamnopyranoside ( 1 ). 相似文献
17.
The Synthesis of 6-substituted 2-Norbornanols The preparation of several 6-exo- and 6-endo-substituted 2-exo- and 2-endó-norbornanols and their p-toluenesulfonates is described. 相似文献
18.
Drevogenin A was converted in several steps (acetylation, hydrogenation, dehydration, hydrogenation, the haloform reaction and energetic alkaline hydrolysis) into 3β, 11α, 12β-trihydroxy-5α-etianic acid, which could be characterised by its crystalline methyl ester ( 15 ) and its tri-O-acetyl methyl ester ( 16 ). The same acid was obtained by partial synthesis starting from hecogenin. Taking into consideration earlier results [1], the structure of drevogenin P is proved to be 3β, 11α, 12β, 14β-tetrahydroxy-20-oxo-Δ5-pregnene ( 7 ). Energetic hydrolysis of dihydro-3-O-acetyldrevogenin A gave a mixture of 17αH- and 17βH-desacyl-kondurangogenin A, which were obtained in crystalline form after separation by chromatography. The only difference between the basic structures of the drevogenins and kondurangogenin A is the presence of a double bond in the 5-position in the former. 相似文献
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