1992 Volume 40 Issue 12 Pages 3261-3268
The reactions of β-and α-pyranose with PCl5 gave products regioselectively chlorinated. The reactions of 1, 2, 3, 4, 6-penta-O-acetyl-β-D-glucopyranose (5) and -β-D-galactopyranose (6) with PCl5 in CCl4 and that of methyl 2, 3, 4-tri-O-acetyl-β-D-glucuranatopyranose (7) with PCl5 in toluene gave 2-O-trichloroacetyl-β-D-pyranosyl chlorides 4, 12 and 14, respectively, as major products, and α-D-pyranosyl chlorides 11, 13 and 15, respectively, as minor products. On the other hand, the reactions of compounds 8 and 9 which were α-anomers of 5 and 6, respectively, with PCl5 gave as major products transformed acetyl groups at C-6 to -C(Cl)=CCl2 or -C(Cl)2-CCl3 group (16 and 17 from 8 and 18 from 9). The same reaction of 10, which was α-anomer of 7, gave α-chloride 15 as major product. The glycosidation of sugar derivative 4 with sarsasapogenin 23 gave β-glycoside 24 (29.1%) and α-glycosides 25 (46.9%), and that of 12 with 23 gave β-glycoside 26 (24.0%) and α-glycoside 27 (40.8%). The improvement of the yields of β-glycosides 24 and 26 (66.9 and 62.1% for 24 and 26, respecitvely) in the glycosidations were accomplished by the employment of α-bromides 28 and 29 obtained from 4 and 6, respectively. The glycosidations of monoglycosides 30 and 31 obtained by the treatment 24 and 26, respectively, with ammonia-saturated ether with sugar acetate bromides 32 and 34 gave diglycoside derivatives 35 and 33, respectively.
