1,1'-(1,6-Dioxo-1,6-hexanediyl)bis-D-proline 224624-80-0 CPOHPC acid D-Proline, 1,1'-(1,6-dioxo-1,6-hexanediyl)bis- R-1-(6-(R-2-carboxypyrrolidin-1-yl)-6-oxohexanoyl)pyrrolidine-2-carboxylic acid Ro 63-8695 cphpc