1-(β-d-Erythrofuranos­yl)cytidine (β-erythrocytidine)

1‐(β‐d‐Erythrofuranosyl)cytidine, C8H11N3O4, (I), a derivative of β‐cytidine, (II), lacks an exocyclic hydroxy­methyl (–CH2OH) substituent at C4′ and crystallizes in a global conformation different from that observed for (II). In (I), the β‐d‐erythrofuranosyl ring assumes an E3 conformation (C3′‐exo; S, i.e. south), and the N‐glycoside bond conformation is syn. In contrast, (II) contains a β‐d‐ribofuranosyl ring in a 3T2 conformation (N, i.e. north) and an anti‐N‐glycoside linkage. These crystallographic properties mimic those found in aqueous solution by NMR with respect to furan­ose conformation. Removal of the –CH2OH group thus affects the global conformation of the aldofuranosyl ring. These results provide further support for S/syn–anti and N/anti correlations in pyrimidine nucleosides. The crystal structure of (I) was determined at 200 K.