Synthesis of push-pull derivatives of levoglucosenone as precursors of annellated pyranosides

1,6-Anhydro-3-deoxy-4-S-ethyl-4-thio-beta-D-erythro-hexopyranos-2-ulose (2) reacted with carbon disulphide and iodomethane to furnish 1,6-anhydro-3-[b is(methylthio)methylene]-3-deoxy-4-S-ethyl-4-thio-beta-D-erythro-hexopyrano s-2-ulose (3). Treatment of 2 with dimethylformamide dimethyl acetal yielde d 1,6-anhydro-3-deoxy-3-(dimethylaminomethylene)-4-S-ethyl-4-thio-beta-D-er ythro-hexopyranos-2-ulose (4). The reactions of 3 with malononitrile and hy drazine hydrate furnished 1,6-anhydro-3-[bis-(methylthio)methylene]-2-(dicy anomethylene)-2,3-dideoxy-4-S-ethyl-4-thio-beta-D-erythro-hexopyranose (7) and (1R,7R,8R)-2,3,5,6(2,4,5,6)-tetradehydro-7-ethylthio-5- methylthio-3,4- diaza-10,11-dioxatricyclo[6.2.1.0(2,6)]undecane (8a, b), respectively.