The stereoselective synthesis of 4'-β-thioribonucleosides via the pummerer reaction

Journal of the American Chemical Society

Volumn 122, Issue 30, 2000, Pages 7233-7243

  Naka, Takashi ^a   Minakawa, Noriaki ^a   Abe, Hiroshi ^a   Kaga, Daisuke ^a   Matsuda, Akira ^a  

^a HOKKAIDO UNIVERSITY   (Japan)

Author keywords

[No Author keywords available]

Indexed keywords

1,2 DICHLOROETHANE; ACETONITRILE; ADENOSINE DERIVATIVE; AMMONIA; AMMONIUM FLUORIDE; CYTOSINE DERIVATIVE; PURINE DERIVATIVE; RIBONUCLEOSIDE DERIVATIVE;

ARTICLE; CHEMICAL MODIFICATION; CHEMICAL REACTION; CHEMICAL STRUCTURE; DIASTEREOISOMER; OXIDATION; REACTION ANALYSIS; STEREOCHEMISTRY; SYNTHESIS;

EID: 0034596301     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja000541o     Document Type: Article

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48. 3,4 of R-10 were 0 and 12.0 Hz, and those of S-10 were 0.9 and 10.3 Hz, respectively. Consequently, the sugar pucker modes of R-10 and S-10 were both estimated to be preferentially C-3-endo conformations.
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54. 6-benzoyladenine gave the coupling product in 66% yield as a mixture of regioisomers, which probably correspond to N-3, N-7, and the desired N-9 isomers. However, the resulting mixture was inseparable, and the N-9 isomer was not obtained preferentially under any conditions.
55. The assignment of the configuration at the anomeric carbon as α or β has been often based on the splitting pattern of H-1′. In the ribonucleosides possessing 1,1,3,3-tetraisopropyldisiloxane-1,3-diyl group on their 3′- and 5′-hydroxyl groups, a somewhat broad singlet is generally observed for the β isomer, while a doublet is observed for the α isomer. In comparison with those of 11 and 18, the same tendency appeared to be maintained in the 4′-thioribonucleoside analogues.
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59. When 26 was treated with methanolic ammonia, a 6-methoxypurine derivative was observed along with the 4′-thioadenosine (27).
60. 2 at room temperature, the N-7 isomer was obtained in 58% yield preferentially. The UV spectrum of the N-7 isomer in MeOH showed absorption maxima at 325, 294, and 256 nm. Among them, the maximum at 325 nm is characteristic of the N-7 glycosyl isomers of 2-amino-6-chloropurine; see: Hanna, N. B.; Ramasamy, K.; Robins, R. K.; Revankar, G. R. J. Heterocycl. Chem. 1988, 25, 1899-1903.
61. The UV spectrum of 28 in MeOH showed absorption maxima at 315 (shoulder), 298, and 256 nm; see ref 36.