合成路线1

The preparation of the cyclopentylamino intermediates (I) and (XIX) is shown in Scheme 4. Reaction of (1S,4R)-4-acetoxy-2-cyclopentenol (XXX) with di-tert-butyl iminodicarboxylate in the presence of NaH and Pd(PPh3)4 produces the di-Boc-protected aminocyclopentenol (XXXI), which undergoes dihydroxylation to triol (XXXII) by means of N-methylmorpholine N-oxide and a catalytic amount of osmium tetroxide. After acidic deprotection of the di-Boc derivative (XXXII), the resulting amino triol (XXXIII) is converted to the key acetonide (I) upon heating with 2,2-dimethoxypropane and catalytic HCl in acetone (1, 2). The O-hydroxyethyl derivative (XIX) is prepared by protection of aminoalcohol (I) as the benzyl carbamate (XXXIV), followed by O-alkylation with ethyl bromoacetate and potassium tert-butoxide to give (XXXV). Subsequent reduction of ester (XXXV) with LiBH4 in THF furnishes the corresponding hydroxyethyl derivative (XXXVI), from which the N-(benzyloxycarbonyl) group is removed by catalytic hydrogenation over Pd/C (3). Scheme 4.