Facile Synthesis of Tumor‐Associated Carbohydrate Antigen Ganglioside GM 3 from Sialic Acid, Lactose, and Serine

Ganglioside GM 3 [α‐Neu5Ac‐(2,3)‐β‐Gal‐(1,4)‐β‐Glc‐(1,1)‐Cer; 1 ] is considered as an important tumor‐associated carbohydrate antigen, which can be used in the development of tumor vaccine. In this study, a facile and convergent synthetic strategy for GM 3 was developed, and the preparation of three building blocks started from the most readily available compounds sialic acid, lactose, and L ‐serine. Ceramide aglycon 9 was constructed from L ‐serine in 13 steps with 6 % overall yield, and lactosyl trichloroacetimidate 14 was synthesized from lactose in 7 steps with 25 % yield. With novel N ‐acetyl‐5‐ N ,4‐ O ‐oxazolidinone protected p ‐toluenethiosialoside 15 as donor, which was developed by our group, the sialylation of benzoyl‐protected lactosyl ceramide diol 23 was successfully accomplished in 54 % yield. Our strategy here provides a shorter linear total synthesis of GM 3 in five steps and with 26 % overall yield. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)