(+)-1-[(3R,3aS,5aR,6R,9bS)-6-Hydroxy-5a,9-dimethyl-2-oxo-2,3,3a,4,5,5a,6,7,9a,9b-decahydronaphtho[1,2-b]furan-3-ylmethyl]pyrrolidine-2(S)-carboxylic acid