Sulfuric Acid → Allyl(5S)-5-hydroxy-2,3,4-tri-O-benzyl-alpha-D-xylopyranoside

Participants

Reaction Steps

At -78°, DIBAH (2.8 ml of a 20% solution in toluene, ca. 2.9 mmol) was added dropwise to a solution of 7 (553 mg, 0.96 mmol) in CH2Cl2 (20 ml). After 15 min., a sat. solution of NH4Cl (2 ml) was added. The mixture was warmed up to r.t., diluted with H2O and a 1M solution of H2SO4 (10 ml). The aq. layer was extracted with CH2Cl2 (3×), the combined org. layers were extracted with brine (2×), dried (MgSO4) and evaporated to yield 499 mg (98%) of crystalline 8 which was used without further purification in the next step. Rf (EtOAc/hexane 1:2) 0.32. 1H-NMR (300 MHz, CDCl3): 2.92 (broad s, OH); 3.33 (dd, J=9.2, 7.8, H--C (4)); 3.60 (dd, J=9.7, 3.7, H--C (2)); 3.99 (t, J=9.5, H--C (3)); 4.07 (ddt, J=12.9, 6.6, 1.2, OAll); 4.23 (ddt, J=12.9, 5.2, 1.4, OAll); 4.65 (d, J=12.0), 4.79 (d, J=12.0, PhCH2); 4.78 (d, J=3.7, H--C (1)); 4.81 (d, J=11.2), 4.89 (d, J=11.9, PhCH2); 4.85 (d, J=10.9), 4.93 (d, J=10.9, PhCH2); 5.06 (d, J=7.8, H--C (5)); 5.24 (dq, J=10.3, 1.5, OAll); 5.34 (dq, J=17.2, 1.5, OAll); 5.93 (dddd, J=17.1, 10.3, 6.6, 5.2, OAll); 7.28-7.42 (m, 15 arom. H).

Provenance & Evidence