Communications Scheme 3. Syntheses of hexose-type peracetylated ANSs through five sequential Overman rearrangements. A) Synthesis of D-galactofuranose-type pAc-ANS. B) Synthesis of D-glucofuranose-type pAc-ANS. Scheme 4. Transformation of D-arabinofuranose-type pAc-ANS (22). Boc = tert-butoxycarbonyl, DMAP = 4-dimethylaminopyridine, MS = molecular sieves, TMS = trimethylsilyl.

Abstract:The palladium-catalyzed deracemization of N-protected alkyl carbonates of 5-hydroxy-3-piperidenes by use of chiral phosphine ligands is described. A Trost ligand such as (R)-BPA was found to be a suitable chiral ligand for the deracemization, providing N-protected 5-hydroxy-3-piperidenes in good yields with good to high enantioselectivities. A plausible mechanism for the reaction is proposed.

Scheme 3. Syntheses of hexose-type peracetylated ANSs through five sequential Overman rearrangements. A) Synthesis of D-galactofuranose-type pAc-ANS. B) Synthesis of D-glucofuranose-type pAc-ANS. Scheme 4. Transformation of D-arabinofuranose-type pAc-ANS (22). Boc = tert-butoxycarbonyl, DMAP = 4-dimethylaminopyridine, MS = molecular sieves, TMS = trimethylsilyl.

Saponins exhibit multiple biological and pharmacological activities, and sugar moiety of saponins have been known to play a crucial role in bioactivity. In this report, we focus on the synthesis and evaluation of saponins with all-nitrogenated sugar (ANS), in which all oxygens are replaced with nitrogens. OSW-1 derivative-, cholesterol-, and diosgenin-ANS glycosides are synthesized by glycosylation with ANS in the presence of TMSOTf. As a result, OSW-1 mimic with ANS exhibits good cytotoxic activity (IC50 = 7.31 µM) and induces apoptosis.

All-nitrogenated sugars … … (ANSs), in which all hydroxy groups in a carbohydrate are replaced with amino groups, are anticipated to be privileged structures with useful biological activities. In