Both anomers of methyl 1-thio-L-rhamnopyranosides were prepared through methylation of the corresponding isothiouronium salt. 2, 3-0-Isopropylidene-, benzylidene- and the until now unknown diphenyl-methylene acetals were synthesized. Phase-transfer catalysed benzylation and LiAlH4-AlCl3-,-type hydrogenolysis of benzylidene acetals were used to obtain partially benzylated derivatives. Comparing the 13C NMR data of the synthesized compounds with those of their 0-glycoside analogues revealed that the O→S exchanges at the anomeric centres caused drastic upfield shifts (~15 ppm) at C-l and moderate downfield shifts at C-2 and C-5, as well. The chemical shift values of other carbons are not sensitive to the O→S replacement.
ASJC Scopus subject areas
- Organic Chemistry