Determination of the stereochemistry of γ-Butyrolactones by DPFGSE-NOE experiments

The stereochemistry of γ-butyrolactons tetrahydro-6a-phenylfuro[3,4-b]furan-2(3H)-one (1), 1,4,5,9b-tetrahydro-3a-methylnaphtho[2,1-b]furan-2(3aH)-one (2), 1,4,5,9 b-tetrahydro-3a-methylfuro[2,3-c]quinolin-2(3aH)-one (3) and hexahydro-furo[3,2-c]benzofuran-2-one (4) was studied using DPFGSE-NOE experiments. Compounds 1–3 contain two stereocenters, while 4 contains three. Both 1H and 13C spectra showed a single diastereomer of all the compounds. Routine 2D experiments (DQF)-COSY, HMQC/HSQC, and HMBC were used to assign 1H and 13C spectra completely. Diastereotopic methylene protons with resolved 1H NMR signals as well as protons of cyclohexane served as references for the construction of the spatial arrangement in the molecules. NOE contacts between protons attached to the stereocenter and the diastereotopic protons were thus used to determine the configuration of the molecules. Vicinal coupling constants 3J assisted the assignment of the conformational arrangement of the cyclohexane ring of 4. Copyright © 2007 John Wiley & Sons, Ltd.