Total Asymmetric Syntheses of 1,5-Dideoxy-1,5-iminooctitols and 1,2,6,7,8-Pentahydroxyindolizidines
作者:Yuanwei Chen、Pierre Vogel
DOI:10.1021/jo00088a033
日期:1994.5
(1R,4R,5S,6S,7S)-4-exo-[(1'S,2'R)-1'-Hydroxy-2',3'-(isopropylidenedioxy)propyl]-6-exo,7-exo-(isopropylidenedioxy)-2,8-dioxabicyclo[3.2.1]octan-3-one ((+)-5) and its diastereomer (1S,4S,5R,6R,7R)-(1'R,2'R)-(-)-30 derived from (R)-2,3-O-isopropylideneglyceraldehyde and (+/-)-5-exo,6-exo-(isopropylidenedioxy)-7-oxabicyclo[2.2.1]hept-2-one were alcoholyzed with benzyl alcohol in CCl4 (CsF as base) into the corresponding 5-C-(benzyloxycarbonly)-5-deoxyoctofuranoses (+)-9 and (-)-31 which were converted via Curtius rearrangements into (-)-1,5-dideoxy-1,5-imino-D-erythro-D-talo-octitol ((-)-20) and its D-threo-L-talo isomer (+)-36, respectively, Alcoholyses of (+)-5 and (-)-30 with benzyl alcohol in DMSO in the presence of CsF or K2CO3 led to the epimerized benzyl esters (-)-10 and (-)-38, respectively, which were converted into (-)-1,5-didoexy-1,5-imino-D-erythro-6-allo-octitol ((-)-27) and its D-threo-D-allo isomer (+)-42. The 1,5-dideoxy-1,5-iminooctitols were converted into the corresponding 1,2,6,7,8-pentahydroxyindolizidines in a single step.
(1R,4R,5S,6S,7S)-4-exo-[(1'S,2'R)-1'-羟基-2',3'-(异丙叉二氧基)丙基]-6-exo,7-exo-(异丙叉二氧基)-2,8-二氧杂双环[3.2.1]辛烷-3-酮 ((+)-5) 及其对映体 (1S,4S,5R,6R,7R)-(1'R,2'R)-(-)-30,源自 (R)-2,3-O-异丙叉甘油醛和 (+/-)-5-exo,6-exo-(异丙叉二氧基)-7-氧杂双环[2.2.1]庚-2-酮,经在四氯化碳(铯氟化物作为碱)中与苯甲醇进行醇解,生成相应的 5-C-(苯甲氧基羰基)-5-去氧代八糖呋喃糖苷 (+)-9 和 (-)-31。后者经卡特里乌斯重排转化为 (-)-1,5-二去氧-1,5-亚胺-D-赤-L-塔罗八糖醇 ((-)-20) 和其 D-赤-L-塔罗异构体 (+)-36。此外,(+)-5 和 (-)-30 在二甲基亚砜中、在铯氟化物或碳酸钾存在下与苯甲醇醇解,生成构型互变的苯甲酸酯 (-)-10 和 (-)-38,进而转化为 (-)-1,5-二去氧-1,5-亚胺-D-赤-6-阿洛八糖醇 ((-)-27) 和其 D-赤-D-阿洛异构体 (+)-42。1,5-二去氧-1,5-亚胺八糖醇随后单步转化为相应的 1,2,6,7,8-五羟基吲哚嗪。