Reaktionen von Amidacetalen

Abstract

Reaktionen von Amidacetalen wie Ketalisierung von Carbonylverbindungen, Veresterung von Carbon,auren, Bildung von Phenolathern sowie Konfigurationsumkehr von 3-Hydroxysteroiden werden teschrieben sowie ihre Mechanismen und Nebenreaktionen diskutiert. -Das Dimethylacetal des N-Formylpyrrolidins verestert 4-Nitrobenzoesaure nicht nur schneller, sondern wegen der verminderten Nebenreaktionen auch in hoheren Ausbeuten als das gewohnlich benutzte Dimethylacetal des Dimethylformamids. Reactions of Amide AcetalsReactions of amide acetals, e. g. ketalisation of carbonyl compounds, esterification of carboxylic acids, formation of phenolic ethers and inversion of 3-hydroxy steroids are described and their mechanisms and side reactions discussed. -The dimethyl acetal of N-formylpyrrolidine esterifies 4-nitrobenzoic acid not only faster but, owing to diminished side reactions, also in higher yields compared to the commonly used dimethyl acetal of dimethylformamide.

Pyrazolo[3,4-d]pyrimidine ribonucleosides as anticoccidials. 2. Synthesis and activity of some nucleosides of 4-(alkylamino)-1H-pyrazolo[3,4-d]pyrimidines

“…Among the monosubstituted straight-chain analogues (5-7, 10, 11, 13, and 14), only the ethylamino (6) and phenethylamino ( 14) derivatives showed slight activity. In this series, branching adjacent to the nitrogen as in the cyclopentylamino derivative (8) or disubstitution on nitrogen (15, 16, and 18) was tolerated, and these derivatives were among the most active in vivo. This is in contrast to the 4-alkylthio series, where branching in the alkyl chain was not tolerated.…”

“…The simplicity of the silylation reaction makes it an attractive method for the synthesis of ribonucleosides of 4-(alkylamino)-lJT-pyrazolo [3,4-d]pyrimidines. The 4-[(3-methyl-2-butenyl)amino] derivative (9) was prepared using method C. The enzymatic preparation and methylation of 4-(methylthio)-l-j8-D-ribofuranosyl-l/ipyrazolo [3,4-d]pyrimidine that were used in method D (Scheme I) have been reported.1 The displacement of the 4-methylthio group by the appropriate amine was carried out as described in the literature,6® as for 4, or in a slightly modified manner (Syntheses and Experimental Sections) to give the remainder of the known (5,6 12,60 136®) and novel (6,8,(10)(11)(12)14,(16)(17)(18)(19) compounds, with 6 being described in detail.…”

“…(C12H13FN2O7-0.6C2H5OH• 0. 2CHC13) C, , N. l-jd-D-Erythrofuranosyl-5-fluorouracil (8). The diacetate 13 (1.6 g, 5.1 mmol) was dissolved in MeOH (50 mL), and 1 M NaOMe (16 mL) was added.…”

Synthesis of oligoribonucleotides containing isoguanosine

“…-Monomers. Isoguanosine (isoG; 1) was prepared from guanosine via 2-aminoadenosine according to a procedure first developed by Duvoll [3] and using the improved protocol of Vorbriiggen and Krolikiewicz [13] instead of the formerly described synthesis of 2-aminoadenosine [ 141 [15]. Thus, silylation of guanosine with hexamethyldisilazane in the presence of Me,SiCl was followed by amination in a steel vessel affording the 2-aminoadenosine in 68% yield.…”