2,3,4,6-四- ö苄基d -glucitol(5)反应以甲苯p -磺酰基氯在吡啶中于60℃,以形成主要是呋喃产物2,3,6-三ö -苄基-1,4-脱水-D-葡萄糖醇(10)及其5-甲苯-对磺酸酯(11),但失去4- O-苄基。该吡喃产物四ö苄基1,5-脱水- d -glucitol preponderates当中间2,3,4,6-四ö -toluene- p -sulphonyl- d -glucitol(6)转化成其0–5氧阴离子。在新合成的2,3,5-tri- O中已经利用了苄氧基的参与苄基α(及β) - d -ribofuranosylethyne,(20)和(4),从2,3,4,5-四ö苄基醛基- d -核糖。描述了由(20)合成2-α- D-呋喃呋喃糖基马来酰亚胺(Showdomycin的α-异构体)。
Displacement reactions on 2,3,4,6-tetra-O-benzyl-1,5-di-O-sulfonyl-D-glucitols. Synthesis of (3R,4S)-3,4-dibenzyloxy-2-(2-benzyloxyethylidene)tetrahydrofuran
摘要:
Treatment of the 1,5-dimesylate and 1,5-ditosylate of 2,3,4,6-tetra-O-benzyl-D-glucitol 1 with tetrabutylammonium acetate in acetonitrile leads, through nucleophilic attack by O-2 at C-5 and normal displacement at C-1, to 1-O-acetyl-2,5-anhydro-3,4,6-tri-O-benzyl-L-iditol. In contrast, the corresponding 1,5-ditriflate on similar treatment undergoes displacement at C-1 by attack of O-4 and elimination of triflic acid between C-4 and C-5 to afford (3R,4S)-3,4-dibenzyloxy-2-(2-benzyloxyethylidene)tetrahydrofuran.