合成路线1

The precursor (R)-9-[4-hydroxy-2-(hydroxymethyl)]guanine (VI) was prepared by conjugate addition of dimethyl itaconate (II) to 2-amino-6-chloropurine (I), followed by reduction of the resultant diester (III) with LiBH4 to yield (IV). Subsequent displacement of the 6-chloro group of (IV) with ammonia under pressure furnished the racemic 2,6-diaminopurine (V). Then, enantioselective deamination of (V) in the presence of adenosine deaminase provided the target (R)-guanine derivative (VI). Esterification of the 4-hydroxy group of (VI) with N-Boc-L-valine (VII) by means of DCC gave the valine ester (VIII). The remaining free hydroxyl group of (VIII) was further esterified with stearoyl chloride (IX) in pyridine, yielding stearate (X). Finally, acid-promoted N-Boc group cleavage in (IX) furnished the title compound.