合成路线1

The monoprotection of acetonide dol (I) by means of Pmb-Cl and KOH in refluxing benzene gives the alcohol (II), which is submitted to a Swern oxidation, yielding the aldehyde (III). The Horner Wadswort Emmons condensation of (III) with phosphonate (IV) by means of NaH in THF affords the unsaturated ester (V), which is deprotected by means of HCl in hot ethanol to provide the diol (VI), which is reprotected by means of Tbdms-OTf and TEA in dichloromethane to gives the bis silyl ether (VII).The selective deprotection of (VII) by means of DDQ in aqueous acetonitrile yields the primary alcohol (VIII), which is submitted to a Swern oxidation to afford the corresponding aldehyde (IX). The cyclization of (IX) by means of PhCH2-S-Li in THF provides the chiral cyclopentanol (X), which is desilylated by means of HF in aqueous acetonitrile to give the trihydroxy compound (XI). The vicinal cis diols of (XI) are selectively protected with acetone and Ts-OH to yield the acetonide (XII), which is desulfurized by oxidation with NaIO4 and heating at 180 C in decalin to afford the cyclopentenol (XIII). The oxidation of (XIII) by means of PDC in dichloromethane provides the cyclopentenone (XIV), which is reduced at the ester and ketone groups by means of DIBAL in toluene to give the diol (XV). The selective silylation of the primary OH group of (XV) by means of Tbdms-Cl, TEA and DMAP in dichloromethane yields the primary silyl ether (XVI), which is condensed with adenine (XVII) by means of DIAD and PPH3 in THF to afford the protected adduct (XVIII). Finally this compound is deprotected by means of HCl in methanol to provide the target Neplanocin A.