Crystal structures of the synthetic intermediate 3-[(6-chloro-7 H -purin-7-yl)methyl]cyclobutan-1-one, and of two oxetanocin derivatives: 3-[(6-chloro-8,9-dihydro-7 H -purin-7-yl)methyl]cyclobutan-1-ol and 3-[(6-chloro-9 H -purin-9-yl)methyl]cyclobutan-1-ol

Abstract

The crystal structures of an intermediate, C10 H9 ClN4 O 3-[(6-chloro-7H-purin-7-yl)methyl]cyclobutan-1-one (I), and two N-7 and N-9 regioisomeric oxetanocin nucleoside analogs, C10 H13 ClN4 O3-[(6-chloro-8,9-dihydro-7H-purin-7-yl)methyl]cyclobutan-1-ol (II) and C 10 H 11 ClN 4 O, 3-[(6-chloro-9H-purin-9-yl)methyl]cyclobutan-1-ol (IV), are reported. The crystal structures of the nucleoside analogs confirmed the reduction of the N-7- and N-9-substituted cyclobutanones with LiAl(OtBu) 3 to occur with facial selectivity, yielding cis-nucleosides analogs similar to those found in nature. Reduction of the purine ring of the N-7 cyclobutanone to a dihydropurine was observed for compound (II) but not for the purine ring of the N-9 cyclobutanone on formation of compound (IV). In the crystal of (I), molecules are linked by a weak Cl...O interaction, forming a 2 1 helix along [010]. The helices are linked by offset π-π interactions [intercentroid distance = 3.498 (1) Å], forming layers parallel to (101). In the crystal of (II), molecules are linked by pairs of O - H...N hydrogen bonds, forming inversion dimers with an R 2 2 (8) ring motif. The dimers are linked by O - H...N hydrogen bonds, forming chains along [001], which in turn are linked by C - H...π and offset π-π interactions [intercentroid distance = 3.509 (1) Å], forming slabs parallel to the ac plane. In the crystal of (IV), molecules are linked by O - H...N hydrogen bonds, forming chains along [101]. The chains are linked by C - H...N and C - H...O hydrogen bonds and C - H...π and offset π-π interactions [intercentroid distance = 3.364 (1) Å], forming a supramolecular framework.