Lagoden dimethylformamide hemisolvate dihydrate: absolute configuration, dipolar interactions and hydrogen-bonding interactions
Abstract
Lagoden (L.3H2O, where L is Na+.C20H33O6-; sodium 3beta,16,18-trihydroxy-8,13-epi-9,13-epoxylabdan-15-oate trihydrate) is widely used as an effective haemostatic agent. It has been crystallized from dimethylformamide (DMF) as sodium 3beta,16,18-trihydroxy-8,13-epi-9,13-epoxylabdan-15-oate dimethylformamide hemisolvate dihydrate, Na+.C20H33O6-.0.5C3H7NO.2H2O or L2.DMF.4H2O, and the asymmetric unit contains two of the latter formulation. The four symmetry-independent Na+ cations and lagoden anions, one DMF molecule and six of the eight symmetry-independent water molecules assemble into a one-dimensional polymeric structure via dipolar and hydrogen-bonding interactions. The lagoden anions coordinate to the Na+ cations via the carboxylate groups and the two primary hydroxy groups, whereas the secondary OH groups are solely involved in hydrogen bonding. Two of the four symmetry-independent lagoden anions act in a chelating mode, forming seven-membered chelate rings. The absolute structure, based on anomalous dispersion data collected at 130 K with Cu Kalpha radiation, confirms an inverted configuration at chiral centres C8 and C13 (labdane numbering) relative to the labdane skeleton.