Ingrid 't Hart

30 Chapter 2 2 Scheme 1. Chemoenzyma�c synthesis of DSGb5. ( A ) Chemical synthesis of Gb5. Reagents and condi�ons: (a) TMSOTf, CH 2 Cl 2 , 4 Å MS, −35 °C; (b) i. 80% AcOH, 80 °C, ii. Ac 2 O, pyridine, DMAP; (c) i. HF·pyridine, pyridine, ii. Cs 2 CO 3 , Cl 3 CCN, CH 2 Cl 2 , 0 °C; (d) NIS, TfOH, CH 2 Cl 2 , 4 Å MS, −30 °C; (e) DDQ, CH 2 Cl 2 /PBS buffer; (f) TMSOTf, CH 2 Cl 2 , 4 Å MS, −30 °C; (g) i. HF·pyridine, ii. NaOH, THF, 80 °C, iii. Ac 2 O, pyridine, iv. CAN, CH 3 CN/H 2 O, 0 °C (for 16a and 16b ), v. NaOMe, MeOH, vi. Pd(OH) 2 /C, H 2 , MeOH/H 2 O/AcOH. ( B ) Enzyma�c extension to produce DSGb5. Reagents and condi�ons: (a) ST3Gal1, CMP-Neu5Ac, CIAP, MgCl 2 (20 mM), sodium cacodylate buffer (50 mM, pH 7.5), 37 °C; (b) ST6GalNAc5, CMP-Neu5Ac, CIAP, MgCl 2 (20 mM), sodium cacodylate buffer (50 mM, pH 7.5), 37 °C. β 4 α 4 β 3 β 3 α 3 β 4 α 4 β 3 β 3 α 3 α 6 R R 4a,b a b 5a : R = H, 53% 5b : R = (CH 2 ) 5 NH 2 , 69% 6a : R = H, 50% 6b : R = (CH 2 ) 5 NH 2 , 57% 9 10 O O O HO TrocHN OTDS OC(NH)CCl 3 O AcO OAc AcO AcO O R 1 O OR 2 O TrocHN O AcO OAc AcO AcO OC(NH)CCl 3 11 12a: R = pMP 12b: R = (CH 2 ) 5 NBnCbz O O OBn BnO OBn OR O HO OBn BnO BnO O O O NapO BnO Si SPh O O O NapO BnO O O OBn BnO OBn OR O O OBn BnO BnO Si 8a: R = pMP, 52% 8b: R = (CH 2 ) 5 NBnCbz, 59% O R 1 O OR 2 O TrocHN O AcO OAc AcO AcO O O O O BnO O O OBn BnO OBn OR O O OBn BnO BnO Si 16a: R 1 :R 2 = CHPh, R = pMP, 37% 16b: R 1 = R 2 = Ac, R = pMP, 52% 16c: R 1 :R 2 = CHPh, R = (CH 2 ) 5 NBnCbz, 42% O HO OH O AcHN O HO OH HO HO O HO OH O HO O O OH HO OH O O OH HO HO OR 13: R 1 :R 2 = CHPh, 56% 14: R 1 = R 2 = Ac, 86% O R 1 O OR 2 O TrocHN O AcO OAc AcO AcO OTDS 7a: R 1 :R 2 = CHPh, 71% 7b: R 1 = R 2 = Ac, 58% 7a + 8a 7b + 8a 7a + 8b 4a: R = H, 53% 4b: R = (CH 2 ) 5 NH 2 ,19% Ph 15a: R = pMP, 90% 15b: R = (CH 2 ) 5 NBnCbz, 60% 9 + 10 11 + 12a 11 + 12b a b c d e O O O HO BnO O O OBn BnO OBn OR O O OBn BnO BnO Si f g Glc Gal GalNAc Neu5Ac