The C1-C2-O2-H torsion angle q 2 , measured using the atomic coordinates in Table , was -75.52 ± 3°. Table . Atomic coordinates and equivalent isotropic displacement parameters (Å2) for 1 . U (eq) is defined as one third of the trace of the orthogonalized Uij tensor. Compound 1 . Compound 1 was dissolved in a concentrated solution of ~95:5 methanol:water with heat and crystalized at RT via slow evaporation. The structure (tt2202) was re-determined at low temperature to obtain more accurate exocyclic torsion angles involving the hydroxyl hydrogens. The re-determined structure was essentially identical to those reported previously. The presence of C labeling in the compound did not alter the crystal structure in any appreciable fashion. Hydroxyl hydrogen atoms were located from a difference Fourier map and refined freely. The C1-C2-O2-H torsion angle q 2 , measured using the atomic coordinates in Table , is -75.55 ± 3°. Table . Atomic coordinates and equivalent isotropic displacement parameters (Å2) for 1 (tt2202). U (eq) is defined as one third of the trace of the orthogonalized Uij tensor. Compound 2 . Compound 2 was dissolved in a concentrated solution of ~95:5 methanol:water with heat and crystalized at RT via slow evaporation. The structure (tt2203) was re-determined at low temperature to obtain more accurate exocyclic torsion angles involving the hydroxyl hydrogens. The re-determined structure was essentially identical to those reported previously. The presence of C labeling in the compound did not alter the crystal structure in any appreciable fashion. Hydroxyl hydrogen atoms were located from a difference Fourier map and refined freely. The C1-C2-O2-H torsion angle q 2 , measured using the atomic coordinates in Table , is 92.57 ± 3°. Table . Atomic coordinates and equivalent isotropic displacement parameters (Å2) for 2 . U (eq) is defined as one third of the trace of the orthogonalized Uij tensor. Compound 2 . Compound 2 was dissolved in a concentrated solution of ~95:5 methanol:water with heat and crystalized at RT via slow evaporation. The structure (tt2104) was re-determined at low temperature to obtain more accurate exocyclic torsion angles involving the hydroxyl hydrogens. The re-determined structure was essentially identical to those reported previously. The presence of C labeling in the compound did not alter the crystal structure in any appreciable fashion. Hydroxyl hydrogen atoms were located from a difference Fourier map and refined freely. The C1-C2-O2-H torsion angle q 2 , measured using the atomic coordinates in Table , is 92.90 ± 3°. Table . Atomic coordinates and equivalent isotropic displacement parameters (Å2) for 2 (tt2104). U (eq) is defined as one third of the trace of the orthogonalized Uij tensor. Compound 3 . Compound 3 was dissolved in a concentrated solution of ~95:5 methanol:water with heat and crystalized at RT via slow evaporation. The structure (tt2102) was re-determined at low temperature to obtain more accurate exocyclic torsion angles involving the hydroxyl hydrogens. The re-determined structure was essentially identical to those reported previously. The presence of C labeling in the compound did not alter the crystal structure in any appreciable fashion. Hydroxyl hydrogen atoms were located from a difference Fourier map and refined freely. The C1-C2-O2-H torsion angle q 2 , measured using the atomic coordinates in Table , is 123.86 ± 3°. Table . Atomic coordinates and equivalent isotropic displacement parameters (Å2) for 3 . U (eq) is defined as one third of the trace of the orthogonalized Uij tensor. Compound 4 . Compound 4 was dissolved in a concentrated solution of ~95:5 methanol:water with heat and crystalized at RT via slow evaporation. The structure (tt2103) was re-determined at low temperature to obtain more accurate exocyclic torsion angles involving the hydroxyl hydrogens. The re-determined structure was essentially identical to those reported previously. The presence of C labeling in the compound did not alter the crystal structure in any appreciable fashion. Hydroxyl hydrogen atoms were located from a difference Fourier map and refined freely. The C1-C2-O2-H torsion angle q 2 , measured using the atomic coordinates in Table , is 98.69 ± 3°. Table . Atomic coordinates and equivalent isotropic displacement parameters (Å2) for 4 . U (eq) is defined as one third of the trace of the orthogonalized Uij tensor. . Compound 5 1,2 was dissolved in a concentrated solution of ~95:5 methanol:water with heat and crystalized at RT via slow evaporation. The structure (tt2201) was re-determined at low temperature to obtain more accurate exocyclic torsion angles involving the hydroxyl hydrogens. The re-determined structure was essentially identical to those reported previously. The presence of C labeling in the compound did not alter the crystal structure in any appreciable fashion. Hydroxyl hydrogen atoms were located from a difference Fourier map and refined freely. The C1-C2-O2-H torsion angle q 2 , measured using the atomic coordinates in Table , is 169.12 ± 3°. Table . Atomic coordinates and equivalent isotropic displacement parameters (Å2) for 5 . U (eq) is defined as one third of the trace of the orthogonalized Uij tensor. High-resolution 1D 13 C{ 1 H} NMR spectra were obtained on 1-5 using 5-mm NMR tubes on a Varian DirectDrive 600 MHz FT-NMR spectrometer equipped with a 5 mm 1 H-19 F/ 15 N-31 P AutoX dual broadband probe. 1D 13 C{ 1 H} spectra were collected in 2 H 2 O at 20 o C with ~10,000 Hz spectral windows and ~1.5 s recycle times, and were zero-filled twice to give final digital resolutions of ~0.08 Hz per point. Chemical shifts are reported in ppm (d) relative to the 1 H signal of residual D 2 O at δ 4.81 ppm. C- C spin-couplings were obtained by analysis of the doublet character of the two intense signals arising from the mutually coupled C-labeled carbons in each compound (Figures ). Since one of the C-labeled carbons in 1 1,2 , 2 1,2 , 3 1,2 , 4 1,2 and 5 1,2 is an anomeric carbon, non-first-order effects on the measurements of the J CC values were negligible. Since the chemical shifts of C5 and C6 of the C-labeled carbons in 1 and 2 are >1,600 Hz difference in chemical shifts, non-first-order effects on the measurements of the J CC values were negligible.