Synthèse du mèthyl-1 diformyl-2,3 pyrrole,de la méthyl-1 pyrrolo[2,3-d] pyridazine et de la méthyl-1 oxo-6 (6h)cycloheptatrieno[b] pyrrole

This communication describes the synthesis of l-methyl-2,3-diformylpyrrole. This new compound is used to prepare a new heterocycle, l-methylcyclohepta[b]pyrrol-6-one and thus allows a new synthesis of l-methylpyrrolo[2,3-d]pyridazine.     

Chemospecific monofunctionalization of alpha-cyclodextrin in the solid state

[reaction: see text] The properties of the self-assembling aziadamantane inclusion complex with two alpha-cyclodextrin molecules have been exploited to perform a chemospecific monofunctionalization of alpha-cyclodextrin. The insertion of the photochemically generated carbenes takes place chemospecifically into the cyclodextrin's C-3-OH and C-2-OH bonds in 39 and 18% yield, respectively. This model reaction surpasses conventional methods in terms of yield as well as selectivity.     

Synthesis of 2′-amino-2′-deoxy-5-fluorocytidine

Acetylation of 2′-deoxy-5-fluoro-2′-trifluoroacetamidouridine with acetic anhydride in pyridine, followed by treatment with phosphorus pentasulfide in refluxing dioxane afforded 3′,5′-di-O-acetyl-2′-deoxy-5-fluoro-2′-trifluorothioacetamido-4-thiouridine ( 3 ). Treatment of 3 with methanolic sodium methoxide furnished 2′-deoxy-2′-trifluorothioacetamido-4-thiouridine ( 4 ), whereas its treatment with methanolic ammonia gave 2′-amino-2′-deoxy-5-fluorocytidine ( 5 ). An alternative approach for the preparation of this compound proceeding from 2′-trifluoroacetamidocytidine was unsuccessful, since the use of acetic anhydride in pyridine led to the replacement of the trifluoroacetyl function by an acetyl group, yielding an intermediate unsuitable for obtaining the target compound. The title compound was inactive at 1 × 10^?4 M concentration against HeLa and leukemia L1210 cells in vitro, but inhibited the in vitro growth of E. coli cells at a concentration of 1 × 10^?7 M. It was also found to be a substrate for CR/dCR deaminase partially purified from human liver, with a Km of 128 μM.     

Reversal of diastereoselectivities in intra- and intermolecular reactions of 2-adamantanylidenes primarily caused by electron-donating and electron- withdrawing substituents on C5

[reaction: see text] A reversal of diastereoselectivity was observed for novel 5-(trimethylsilyl)adamantan-2-ylidene (1c) with regard to 5-hydroxyadamantan-2-ylidene (1a). Ostensibly in intermolecular reactions, 5-substituted 2-adamantanylidenes (1) are sterically unbiased. However, inductive effects originating from the pendant group bend the divalent carbon bridge of 1 either toward (ERG's, e.g., -Si(CH(3))(3)) or away from (EWG's, e.g., -OH) the gamma-position. Hence, the more exposed side is more susceptible to intermolecular reaction and the other side concomitantly undergoes intramolecular 1,3-CH insertions more readily.     

Über Flächen dritter Ordnung,welche Collineationen in sich zulassen

Ohne Zusammenfassung     

Nuclear spin lattice relaxation of186ReFe and182TaFe: the role of spin wave mechanisms

Using the thermal cycling method, the nuclear spin lattice relaxation of¹⁸⁶ReFe and¹⁸²TaFe has been measured in polarizing fields of 0.1 to 1.2 T. The results for the relaxation constants in the high-field limit are 87(2) and 470(10) ms K, respectively. The relaxation rates are about a factor of three larger than expected from ab initio calculations. It is proposed to interprete this discrepancy as proof for a significant spin wave contribution to the relaxation.     

Synthèse dc la pyrido[2,3-f] phtalazine et des diformyl-6,7; -4,6; -4,7; -2,4 quinoleines

This article describes the synthesis of a new heterocycle, pyrido[2,3,f]phtalazine and three new diformylquinolincs.