Synthesis of clustered xenotransplantation antagonists using palladium-catalyzed cross-coupling of prop-2-ynyl α-D-galactopyranoside
作者:Bingcan Liu、René Roy
DOI:10.1039/b101234g
日期:——
Hyperacute rejection of pig liver transplantation can be antagonized using high affinity anti α-galactoside epitopes (Galα1-3Galβ, Galili antigen). To this end, clusters containing the Galili antigen were synthesized using palladium cross-coupling reactions. Thus, benzyl 3-(O-α-D-galactopyranosyl)-β-D-galactopyranoside derivative 6 was prepared using perbenzylated thiophenyl β-D-galactopyranosyl donor 5 and benzyl 2,6-di-O-benzoyl-α-D-galactopyranosyl acceptor 3. Aglycone interchange from benzyl to prop-2-ynyl disaccharide 8 was successively achieved by hydrogenolysis, peracetylation, regioselective anomeric de-O-acetylation, trichloroacetimidate activation, and finally coupling to propargyl alcohol with triflic acid. The resulting prop-2-ynyl disaccharide 8 was transformed in high yields (>85%) into dimer 10, trimer 12, and tetramer 17 using oxidative homocoupling (10) and palladium-catalyzed aryl iodide cross-coupling (12, 17), respectively. Ester protecting group removal under transesterification conditions afforded fully deprotected α-Gal clusters.
猪肝移植的超急性排斥反应可以通过高亲和力的抗α-半乳糖苷表位(Galα1-3Galβ,Galili抗原)进行拮抗。为此,采用钯交叉偶联反应合成了含有Galili抗原的簇。因此,使用全苄化的噻苯基β-D-半乳糖呋喃糖供体5和苄基2,6-二O-苯甲酰-α-D-半乳糖呋喃糖受体3制备了苄基3-(O-α-D-半乳糖呋喃糖基)-β-D-半乳糖呋喃糖苷衍生物6。通过氢解、过乙酰化、区域选择性的α位去乙酰化、三氯乙酰亚胺活化,最后与丙炔醇在三氟醋酸的存在下偶联,成功实现了苄基到丙-2-炔基二糖8的甾醇交换。所得的丙-2-炔基二糖8以高产率(>85%)转化为通过氧化自偶联获得的二聚体10、三聚体12和四聚体17,分别利用钯催化的芳基碘交叉偶联(12, 17)。在转酯化条件下去除酯保护基团,得到完全去保护的α-Gal簇。