Polyhydroxylated pyrrolidines. Part 4: Synthesis from d-fructose of protected 2,5-dideoxy-2,5-imino-d-galactitol derivatives
作者:Isidoro Izquierdo、María T. Plaza、Miguel Rodríguez、Juan A. Tamayo、Alicia Martos
DOI:10.1016/j.tet.2005.12.023
日期:2006.3
configuration at C(3). Compound 8 was treated with lithium azide yielding 5-azido-4-O-benzyl-5-deoxy-1,2-O-isopropylidene-α-l-tagatopyranose (9) that was transformed into the related 3,4-di-O-benzyl derivative 10. Cleavage of the acetonide in 10 to give 11, followed by regioselective 1-O-pivaloylation to 12 and subsequent catalytic hydrogenation gave (2R,3S,4R,5S)-3,4-dibenzyloxy-2,5-bis(hydroxymethyl
容易获得的3 - O-苯甲酰基-4- O-苄基-1,2- O-异亚丙基-5- O-甲磺酰基-β-d-果糖基吡喃糖(5)直接转化为其d- psico差向异构体(8),后Ó -debenzoylation随后的氧化和还原,这引起了构造的反转在C(3)。用叠氮化锂处理化合物8,得到5-叠氮基-4 - O-苄基-5-脱氧-1,2 - O-异亚丙基-α-1-tag-吡喃葡萄糖(9),将其转化为相关的3,4-二-邻苄基衍生物10。将丙酮化物在10中裂解,得到11,然后进行区域选择性1- O-聚戊二醛化至12,然后进行催化氢化,得到(2 R,3 S,4 R,5 S)-3,4-二苄氧基-2,5-bis (羟甲基)-2'- O-吡咯烷基吡咯烷(13)。O-脱酰基为对称的吡咯烷14后,可以确定13的立体化学。14的总脱保护得到2,5-亚氨基-2,5-二脱氧-d-半乳糖醇(15,DGADP)。