Tohru Saito

Alternative Syntheses of Azepinomycin

Synthese du compose du titre a partir de lamide de lacide formamido-5 O-alkyl alkyl-1 imidazolecarbohydroximique-4 via des alkyl-1 hydroxy-6 hexahydro-3,4,5,6,7,8 imidazo [4,5-e] diazepine-1,4one-8

A Unique Transformation of 5-Amino-N'-methoxyimidazole-4-carboxamidines by Diazotization: Synthesis of the 5-Azido Analogue of ACIA Riboside

Diazotization of 1-substituted 5-amino-N-methoxyimidazole-4-carboxamidines (I) was found to give the 5-azidoimidazole-4-carbonitriles II through the 1-methoxy-2-azaadenine intermediates IV. The product IIb from the riboside Ib was utilized for the synthesis of 5-azido-1-β-D-ribofuranosylimidazole-4-carboxamide (Vb), a novel AICA riboside analogue

Synthesis, ring opening, and glycosidic bond cleavage of 3-methyl-2′-deoxyadenosine

Methylation of N′-benzyloxy-1-(2-deoxy-β-D-ribofuranosyl)-5-formamidoimidazole-4-carboxamidine (2a) followed by hydrogenolysis of the N′-benzyloxy-group and cyclization produced the hitherto unknown 3-methyl-2′-deoxyadenosine (5a), which was readily hydrolysed to 3-methyladenine (6) in H2)O at pH ⩽7·0 and to (6) and the imidazole-(2-deoxy)riboside (4a) at pH 8·98.

A synthetic approach to the marine sponge alkaloids agelasimine A and agelasimine B

Syntheses of 7-benzyl-N 6 ,3-dimethyladenine (1b) and 7-benzyl-1,2-dihydro-1,3-dimethyladenine (2b), selected as models for the marine sponge alkaloids agelasimine A (1a) and agelasimine B (2a), respectively, have been achieved via four-step routes starting from 3-methyladenine (7). The key steps involved are regioselective methylations of 7-benzyl-3-methyladenine (9) and 7-benzyl-1,2-dihydro-3-methyladenine (11)

Synthesis and hydrolysis of 3-methyladenosine

Methylation of N′-benzyloxy-5-formamido-1-β-D-ribofuranosylimidazole-4-carboxamidine (1) followed by hydrogenolysis of the N′-benzyloxy group and cyclization gave the hitherto unknown 3-methyladenosine (4), which was easily hydrolysed to 3-methyladenine (6) in 0·1 N aq. HCl and to the imidazole ribosides (3) and (5) under basic conditions.

Model Experiments for Acetylation of the Marine Sponge Purines Agelasimine-A and Agelasimine-B

Reactions of 7-benzyl-N 6 ,3-dimethyladenine (1b) and 7-benzyl-1,2-dihy- dro-1,3-dimethyladenine (2b), selected as models for the marine sponge alkaloids agelasimine-A (1a) and agelasimine-B (2a), with acetic anhy- dride in pyridine have been studied. The product from (1b) was the imidazole derivative (6b), whose structure was determined by an X-ray crystallographic analysis. The product from (2b) was the N 6 -acetyl derivative (4b). On treatment with boiling H 2 O, (4b) gave 7-benzyl- 2,3-dimethylhypoxanthine (5b) and a compound presumed to be (11)

Synthesis of 3,9-dimethyl- and 3-methyl-9-ethyl-adenine via N′-alkoxy-1-alkyl-5-formamidoimidazole-4-carboxamidine

3,9-Dimethyl- and 3-methyl-9-ethyl-adenine have been synthesized from N′-alkoxy-1-alkyl-5-formamidoimidazole-4-carboxamidine (II) by reduction with LiAIH4 followed by cyclisation with ethyl orthoformate and removal of the alkoxy-group by catalytic hydrogenolysis.

Synthesis of the 1-N-Oxides and 1-Methoxy and N6-Methoxy Derivatives of 2-Deuterioadenines Substituted or Unsubstituted at the 9-Position

Peracid oxidations of adenine-2-d (1a) and its 9-substituted derivatives (1e) produced the corresponding 1-N-oxides (3e) in fair yields. Methylations of 9-methyl- (3b) and 9-benzyladenine-2-d 1-oxide (3e) with MeI in AcNMe 2 afforded the corresponding 1-methoxy derivatives 5b,d and 11e in good yields. Dimroth rearrangement of 5b, 5d, and 11e gave the N 6 -isomers 9b, and 9e, but their isotopic purities were unsatisfactory. Unambiguous assignments of the purine-ring proton signals in the nmr spectra of the unlabeled adenines (4e, 6b,d, and 12e) have been made by comparison with those of the labeled species (3e, 5b,d, and 11e)