Synthesis and Structural Analysis of 5-Deoxy-5-[(rs)-ethylphosphinyl]-α,β-L-idopyranoses

Treatment of (RS)-3-O-acetyl-5-deoxy-5-(ethylmethoxyphosphinyl)-1,2-O-isopropyUdene-α-D-xylo-hexofuranose (5) with dihydropyran in dichloromethane containing pyridinium p-toluenesulfonate gave the 6-O-(tetrahydropyran-2-yl) derivative 7 in 90% yield. Reduction of 7 with sodium dihydrobis(2-methoxyethoxy)aluminate followed by acid hydrolysis preponderantly provided the title compounds, the first unsubstituted L-idopyranoses having a phosphinyl group in the hemiacetal ring. These compounds were converted into four separable 1,2,3,4,6-penta-O-acetates 11a-d, whose structures and⁴C₁(L) conformations were established by spectroscopy.