几种齐墩果酸糖缀合物的合成

Synthesis of Oleanolic Acid Glycoconjugates

报道了齐墩果酸与四种单糖和二糖 (葡萄糖、半乳糖、乳糖及葡萄糖醛酸 )进行糖苷化制备糖缀合物的方法 .在合成过程中首先将葡萄糖、半乳糖及乳糖转化成相应的全苯甲酰三氯亚胺酯糖基供体 (10a～ 10c) ,将葡萄糖醛酸转化成为 1 溴代乙酰葡萄糖醛酸甲酯糖基供体 (10d) ;在齐墩果酸的 2 8 位羧基上进行酰胺化引入ω 氨基羧酸甲酯得到其衍生物 6.然后10a～ 10c在TMSOTf的催化下与化合物 6的 3 位羟基进行 β 糖苷化 ;10d在AgOTf的催化下与 6进行 β 糖苷化 ,最后脱掉保护基得到相应的糖缀合物 13a～ 13d ,所有目的化合物均为新化合物 ,其结构经IR ,1HNMR ,13CNMR ,2D COSY ,HMQC 。

Four glycoconjugates (D-glucose, D-galactose, D-lactose and D-glucuronic acid) of oleanolic acid were synthesized through a facile approach. Firstly, D-glucose, D-galactose and D-lactose were converted into benzoyl group protected glycosyl trichloroacetimidates (10a similar to 10c) as donors. D-glucuronic acid was converted into methyl (tri-O-acetyl-alpha-D-glucopyranosyl bromide) -uronate (10d) as donor. Secondly, oleanolic acid was converted into methyl N-(3-hydroxylolean-12-en-28-oyl)-6-aminohexanoate (6). Then the coupling of the sugar moieties (10a similar to 10c) to 3-OH of 6 was promoted by trimethylsilyl trifluoromethanesulfonate (TMSOTf). AgOTf was used as the promoter in the glycosylation of 10d with 6. Finally, deprotection of the corresponding glycocongjugates afforded the target products 132 similar to 13d. The structures of all products were characterized by IR, H-1 NMR, C-13 NMR, DEPT, tow-dimensional shift-correlated spectra (COSY, HMQC) and HRMS.