Reimei Moroi

Syntheses and alkaline hydrolyses of 2,2′-imino- and 2,2′-(substituted imino)-1-(2′-deoxy-β-D-arabinofuranosyl)uracils

In order to examine the possiblity of ‘up’ amination of the sugar part of pyrimidine nucleosides through pyrimidine N-cyclonucleosides, 2,2′-imino-1-(2′-deoxy-β-D-arabinofuranosyl)uracil (6g) and various N-substituted derivatives of (6g),(6a–f) were synthesized by amination-cyclization reactions of 2′-O-tosyl-2,5′-anhydrouridine (5). The latter was synthesized from 2,5′-anhydrouridine (4) by 2′,3′-O-dibutylstannylation followed by in situ tosylation. N-p-Methoxyphenylisocytidine (7) obtainable from (4) was also cyclized to (6d) by treatment with 1,1′-carbonyldi-imidazole. 2,2′-Arylimino analogues (6c,d) were hydrolysed with 2M NaOH–MeOH (1:1) extremely rapidly to give 2′-deoxy-2′-arylamino uracil-arabinosides (8a,b). The 2′,3′-dideoxy-2′,3′-(N-phenyl)imino analogue of arabinoside (8a), (9), was used for the purpose of structural corroboration of (8a,b). Similar dehydrative cyclization of (6g) gave the 5′,N-anhydro derivative, compound (10), while alkali-treatment gave a fragmentation product, imidazo[1,2-a]pyrimidin-7(8H)-one (11). Spectroscopic arguments which support structures (6), (10), and (11) are also presented.

Dimerization of 2-alkyl-6-methyl-4H-1,3-thiazin-4-ones

Two unusual modes of dimerization of 2-alkyl-6-methyl-4H-1,3-thiazin-4-ones were observed; one gave the linearly combined dimers (3) and the other led to the novel spiro-compound (4); the structure of one of the spiro-compounds (4a) was confirmed by X-ray crystallography.