Synthesis of Novel Anellated Pyranosides as Precursors of C‐Nucleoside Analogues Using Isopropyl 6‐O‐Acetyl‐3‐deoxy‐4‐S‐ethyl‐4‐thio‐α‐D‐threo‐hexopyranosid‐2‐ulose
摘要:
Isopropyl 6-O-acetyl-3-deoxy-4-S-ethyl-4-thio-alpha-D-threo-hexopyranosid-2-ulose (3) was converted to the corresponding 3-[bis(methylthio)methylene] derivative 4 with a push-pull activated C-C double bond. Treatment of 4 with hydrazine and methylhydrazine afforded the pyrano[3,4-c]pyrazol-5-ylmethyl acetates 5a and 5b, respectively. Desulfurization of compound 4 with sodium boron hydride yielded the 3-[(methylthio)methylene]hexopyranosid-2-ulose 7. Compound 7 was reacted with amines to furnish 3-aminomethylene-hexopyranosid-2-uloses 8, 9. Reaction of 7 with hydrazine hydrate, hydrazines, hydroxylamine, and benzamidine afforded the pyrazolo, isoxazalo, and pyrimido anellated pyranosides (10-13).
Michael Addition of Thiols to Sugar Enones. Synthesis of 3-Deoxy-4-Thiohexopyranosid-2-uloses as Key Precursors of 3-Deoxy- and C-2 Branched-Chain 4-Thiosugars