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. 2024 Nov 5;7:252. doi: 10.1038/s42004-024-01337-6

Fig. 5. Synthesis of DE- and CDE-fragments carrying amide replacements.

Fig. 5

Reagents and conditions: (a) NaBH4, AcOH (3 Eq), DCM; (a2) 55, NaBH4, AcOH (3 Eq), DCM; (b) Boc2O, DMAP; (c) Zn/AcOH; (d) AcCl or TMSCl, MeOH; (e) iPrOH (1 Eq), DIAD, PPh3; (f) K2CO3, nicotinic acid; (g) tert-butyl 4-aminobenzoate, P(OPh)3, toluene, reflux; (h) AllBr, K2CO3; (i) LiOH; (j) 4-nitroaniline, T3P, Py; (k) Br2, tBuNH2, toluene/DCM; (l) Ac2O, Py; (m) HNO3, DCM, -40°C; (n) ethynyltrimethylsilane, PdCl2(PPh3)2, CuI, DiPEA; (o) K2CO3, MeOH; (p) 4-azidobenzoic acid, CuSO4, Na-ascorbate, THPTA; (q) 4-nitrobenzoyl chloride, Py, DCM; (r) 72, K2CO3, Pd(PPh3)4, dioxane/H2O; (s) MOM-Br, DMAP, DiPEA; (t) 4-amino tBu benzoate, (COCl)2 or POCl3, DMF (cat.), DCM, Py; (u) HCOOH, Ac2O; (v) EDC, DMAP, tBuOH; (w) 82, POCl3, DiPEA, DCM; (x) +52, NH4OAc, air, H2O; (y) Na2S2O4, EtOH/H2O; (z) 81, air; (a2) allyl chloroformate, DiPEA, 0°C.