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Crystal and Molecular Structure of 6-Thiopurine Riboside

1968; Elsevier BV; Volume: 57; Issue: 7 Linguagem: Inglês

10.1002/jps.2600570714

1520-6017

Eli Shefter,

Biochemical and Molecular Research

The molecular structure of 6-thiopurine riboside (commonly known as 6-mercaptopurine riboside) has been determined by X-ray crystallographic analysis. The material crystallizes from water as orthorhombic needles (space group P212121) with unit cell dimensions of a = 8.622 Å., b = 13.624 Å., and c = 20.262 Å. There are two unique molecules in the asymmetric unit of the cell. The structure was solved by the heavy atom technique and refined by block diagonal least squares. The final R index is 0.067. In general, the bond lengths and angles agree with those found in other nucleoside structures. The C6-S distances of the two molecules (average 1.669 ± 0.002 Å.) together with the presence of a hydrogen on each of the N1 atoms indicates that the molecules are in the thiolactam configuration rather than the mercapto form. The glycosidic torsion angles (φcn) are +135° and +144° for the two molecules. The syn conformation about each of the CN bonds is stabilized by 05′-H…N3 intramolecular hydrogen bonds. The furanose rings are puckered; C2′ being displaced endo in both molecules. Each of the unique sulfurs is involved in a C-H…S interaction, while one is also participating in an O-H…S hydrogen bond. The molecular structure of 6-thiopurine riboside (commonly known as 6-mercaptopurine riboside) has been determined by X-ray crystallographic analysis. The material crystallizes from water as orthorhombic needles (space group P212121) with unit cell dimensions of a = 8.622 Å., b = 13.624 Å., and c = 20.262 Å. There are two unique molecules in the asymmetric unit of the cell. The structure was solved by the heavy atom technique and refined by block diagonal least squares. The final R index is 0.067. In general, the bond lengths and angles agree with those found in other nucleoside structures. The C6-S distances of the two molecules (average 1.669 ± 0.002 Å.) together with the presence of a hydrogen on each of the N1 atoms indicates that the molecules are in the thiolactam configuration rather than the mercapto form. The glycosidic torsion angles (φcn) are +135° and +144° for the two molecules. The syn conformation about each of the CN bonds is stabilized by 05′-H…N3 intramolecular hydrogen bonds. The furanose rings are puckered; C2′ being displaced endo in both molecules. Each of the unique sulfurs is involved in a C-H…S interaction, while one is also participating in an O-H…S hydrogen bond.