The present invention relates to a process for preparing stereoisomerically enriched 4-aryl-4-hydroxybutanoic acid derivatives by reducing 4-aryl-4-ketobutanoic acid derivatives in the presence of ruthenium-containing catalysts. Compositions of the invention should be useful as solvents and, perhaps, as catalysts for many reactions, including aromatic electrophilic substitution, nitration, acylation, esterification, etherification, oligomerization, transesterification, isomerization and hydration. The stent has a high degree of flexibility in the longitudinal direction, yet has adequate vessel wall coverage and radial strength sufficient to hold open an artery or other body lumen. The tone cost of the selected tone is based on a predefined loading frequency and a signal-to-noise ration of the selected tone.