Desymmetrization of cyclohexadienylsilanes. Regio-, diastereo-, and enantioselective access to sugar mimics

Desymmetrization of cyclohexadienylsilanes available from Birch reduction o f the corresponding arylsilanes is efficiently carried out using Sharpless asymmetric dihydroxylation and aminohydroxylation. Complete diastereocontro l and reasonable enantiocontrol have been attained during the preparation o f the desired diols. An excellent regiocontrol has also been observed durin g aminohydroxylation of dienylsilanol 6b. The resulting diol 8 and hydroxyc arbamate 27 have then been elaborated further, offering a straightforward a ccess to various types of cyclitols, aminocyclitols, carbasugars, as well a s the antibiotic palitantine 4. The complete functionalization of the origi nal arylsilanes 5 is thus typically achieved in fewer than eight steps with high stereoselectivities and excellent overall yield.