| Popis: |
The 1,3-dipolar cycloaddition of allyl halides with chiral nitrile oxides, derived from glyceraldehyde derivatives, affords ca. 1:1-mixtures of C5-epimeric isoxazolines. The diastereomers can be separated on a preparative scale by MPLC; the configurations at C5 are established by chemical correlation/X-ray analysis initially, and then routinely, based on consistent, large differences of respective specific rotations. – An unexpected finding, which turned out to be the key to efficient transformation of 5-halomethyl-isoxazolines into hydroxy-pyrrolidines, is that highly stereoselective catalytic hydrogenations are feasible with proper combination of both 3- and 5-side chain structures and the catalyst system. – This (C3 + Cn)-approach is extended to include dihydroxy-pyrrolidines, i. e. 1,4-iminopolyols, and further 1,5-iminopolyols and bicyclic 1,5,8-iminopolyols. The substrates for the latter hydrogenation/cyclization are derived from optically active furoisoxazolines. – Some of the new iminopolyols show strong inhibition of glucosidases. |
