PhI(OAc)2 / I 2促进的在C2具有吸电子基团(EWG)的碳水化合物的异头烷氧基自由基β片段化(ARF)产生无环碘化物,可通过Arbuzov反应将磷的五价原子引入其中。在选择性水解和随后的环化之后,可将膦酸酯或次膦酸酯中间体转化为2-脱氧-1-磷酸杂戊基吡喃糖和2-脱氧-1-磷酸戊烯基吡喃糖。在C2处具有电子给体基团(EDG)的碳水化合物的ARF通过自由基-极性交叉机制进行,并且环化反应是通过方便地定位的膦酸酯或次膦酸酯基团对瞬态氧碳鎓离子的亲核攻击而发生的。这种替代方法导致具有4-脱氧-5-磷酸戊烯基吡喃糖构架的5-磷酸戊糖。2-oxo-1,2-oxaphosphinane和2-oxo-1的结构和构象
Total Syntheses of Tumor-Related Antigens N3: Probing the Feasibility Limits of the Glycal Assembly Method
摘要:
The total syntheses of two octasaccharide antigens isolated from human milk, 1 and 2, and their corresponding allyl glycosides, 3 and 4, have been achieved by utilizing the glycal method, Convergent assembly of the core hexasaccharides and concurrent introduction of two alpha -L-fucosyl moieties at the late stage of the syntheses provided these complex:carbohydrates in a concise manner. With synthetic material obtained, biological evaluations of these antigens as potential gastrointestinal cancer immunotherapeutic agents have been initiated.