合成路线1

Synthesis of intermediates (XX) and (XXIII): Coupling of methyl L-lactate (XII) with morpholine in presence of NaH yields amide (XIII) which is tosylated by means of NaH and p-TsCl in THF to afford (XIV). Reduction of carboxylic acid (XV) in DCE with B(OCH3)3, boron trifluoride diethyl etherate and BH3·pyr complex provides alcohol (XVI) which is then condensed with (XIV) in presence of K2CO3 in DMF to yield (XVII). Mesylation of (XVII) with MsCl in presence of Et3N in CH2Cl2 affords (XVIII), which reacts with potassium phthalimide (C) in DMF to give (XIX). Hydrogenation of phthalimide (XIX) with H2 over Pd/C in DMF provides derivative (XX). The treatment of (XIX) with NH2NH2 and p-TsOH gives amine (XXI), which is protected with di-t-butyl-dicarbonate to yield (XXII). Finally (XXIII) is obtained by reduction of the nitro moiety of (XXII) with H2 over Pd/C in EtOAc.