Regio and stereoselective conversion of Δ4-uronic acids to l-Ido- and d-glucopyranosiduronic acids
摘要:
Synthesis of L-ido- and D-glucopyranosiduronic acids was performed starting from protected Delta(4)-uronic acids 3a-f. Bromination of the C-4,5 double bond provided the trans-diaxial bromohydrin derivatives 6a-d, which were converted to the corresponding epoxides 7a-d in high yields. Direct reduction of these epoxides using borane-tetrahydrofuran complex afforded the o-glucopyranosiduronic acids 9b-d, while Lewis acid rearrangment through the C-4 keto intermediate 10b-d afforded the L-idopyranosiduronic acids 11b-d. (C) 1997, Elsevier Science Ltd.
化学合成了十六种4-尿酸δ单糖。它们的羧基被保护为甲基或苄基酯,异头羟基被保护为苄基糖苷,而2和3个羟基分别被不同的取代方式保护为酯和醚衍生物。由肝素酶制备含4-尿酸δ的二糖。它们的羧基未被保护或被保护为苄基酯,并且在尿酸酯部分中的两个羟基是游离的,因为O-磺基衍生物或被酰化。通过检查质子间的邻位偶合常数,使用1 H NMR研究了这些不饱和尿酸盐单糖和二糖残基的构象。δ4-尿酸酯残基采用2H1或1H2构象。