A new asymmetric synthesis of stavudine has been described: The regioselective epoxidation of allyl alcohol (I) by means of titanium tetraisopropoxide and alpha,alpha-dimethylbenzylperoxide, catalyzed by diisopropyl D-tartrate, followed by esterification with pivaloyl chloride yields the epoxide (II), which is then condensed with lithium acetylide catalyzed by boron trifluoride ethearate in THF, yielding the acetylenic alcohol (III). The cyclization of (III) catalyzed by Mo(CO)6 and trimethylamine oxide affords the dihydrofuran (IV), which is condensed with N,N'-bis(trimethylsilyl)thymine (V) and I2 to give the iodonucleoside (VI). Finally, this compound is dehydroiodinated and deprotected with sodium methoxide in methanol.

The enantioselective epoxidation of allyl alcohol (I) with 2-phenylisopropyl hydroperoxide (II) and Ti(iPrO)4 in the presence of D-diisopropyl tartrate gives the chiral epoxide (III), which is esterified with pivaloyl chloride to yield the pivalate (IV). The opening of the epoxide ring of (IV) by means of lithium acetylide (V) and BF3/Et2O affords the alkynyl alcohol (VI), which is cyclized by means of Mo(CO)6 and trimethylamine oxide to provide the chiral dihydrofuran (VII). The oxidation of (VII) with OsO4 and 4-methylmorpholine-N-oxide (NMMO) gives the diol (VIII), which is treated with Ac2O to yield the diacetate (IX). The condensation of (IX) with N6-benzoyl-N6,7-bis(trimethylsilyl)adenine (X) by means of Tms-OTf affords the nucleoside (XI). Finally, this compound is deprotected by means of NaOMe in methanol.

The reaction of adenosine (I) with 2-acetoxyisobutyryl bromide (A) gives the 3'-bromonucleoside (II) along with some 3'-bromo regioisomer (III). The reaction of the desired isomer (II) with HCl in methanol yields the intermediate acetylated 3'-bromonucleoside (V) and finally the 3'-bromo-3'-deoxyadenosine (VI). This compound is then debrominated by hydrogenation with H2 over Pd/C in ethanol/water.

The reaction of adenosine (I) with triethyl orthoacetate (II) by means of Ts-OH in acetonitrile gives the bicyclic dioxolane (III), which is treated with acetyl bromide in dichloroethane to yield the acetylated bromonucleoside (IV). The debromination of (IV) by means of Bu3SnH in toluene affords the acetylated target compound (V), which is finally deprotected with ammonia in methanol.

The enantioselective epoxidation of allyl alcohol (I) with 2-phenylisopropyl hydroperoxide (II) and Ti(iPrO)4 in the presence of D-diisopropyl tartrate gives the chiral epoxide (III), which is esterified with pivaloyl chloride to yield the pivalate (IV). The opening of the epoxide ring of (IV) by means of lithium acetylide (V) and BF3/Et2O affords the alkynyl alcohol (VI), which is cyclized by means of Mo(CO)6 and trimethylamine oxide to provide the chiral dihydrofuran (VII). The oxidation of (VII) with OsO4 and 4-methylmorpholine-N-oxide (NMMO) gives the diol (VIII), which is treated with Ac2O to yield the diacetate (IX). The condensation of (IX) with N6-benzoyl-N6,7-bis(trimethylsilyl)adenine (X) by means of Tms-OTf affords the nucleoside (XI). Finally, this compound is deprotected by means of NaOMe in methanol.

The reaction of adenosine (I) 2-acetoxyisobutyryl bromide (A) in acetonitrile/water gives a mixture of the 3-bromo (II) and 2-bromo nucleosides (III), which is treated with Dowex (OH), Amberlite (OH) or methanolic NaOMe to yield the epoxide (IV). Finally, this compound is reduced with LiEt3BH in THF/DMSO or LiAlH4 in THF to afford a mixture of the 2'-deoxy nucleoside (V) and the target compound that are separated by chromatography. Alternatively, the mixture of the nucleosides (II) and (III) is debrominated by reaction with Bu3SnH and AIBN in refluxing toluene to give the same mixture of (V) and the target compound that is separated as before.

The reaction of adenosine (I) 2-acetoxyisobutyryl bromide (A) in acetonitrile/water gives a mixture of the 3-bromo (II) and 2-bromo nucleosides (III), which is treated with Dowex (OH), Amberlite (OH) or methanolic NaOMe to yield the epoxide (IV). Finally, this compound is reduced with LiEt3BH in THF/DMSO or LiAlH4 in THF to afford a mixture of the 2'-deoxy nucleoside (V) and the target compound that are separated by chromatography. Alternatively, the mixture of the nucleosides (II) and (III) is debrominated by reaction with Bu3SnH and AIBN in refluxing toluene to give the same mixture of (V) and the target compound that is separated as before.

The reaction of adenosine (I) 2-acetoxyisobutyryl bromide (A) in acetonitrile/water gives a mixture of the 3-bromo (II) and 2-bromo nucleosides (III), which is treated with Dowex (OH), Amberlite (OH) or methanolic NaOMe to yield the epoxide (IV). Finally, this compound is reduced with LiEt3BH in THF/DMSO or LiAlH4 in THF to afford a mixture of the 2'-deoxy nucleoside (V) and the target compound that are separated by chromatography. Alternatively, the mixture of the nucleosides (II) and (III) is debrominated by reaction with Bu3SnH and AIBN in refluxing toluene to give the same mixture of (V) and the target compound that is separated as before.

The reaction of adenosine (I) 2-acetoxyisobutyryl bromide (A) in acetonitrile/water gives a mixture of the 3-bromo (II) and 2-bromo nucleosides (III), which is treated with Dowex (OH), Amberlite (OH) or methanolic NaOMe to yield the epoxide (IV). Finally, this compound is reduced with LiEt3BH in THF/DMSO or LiAlH4 in THF to afford a mixture of the 2'-deoxy nucleoside (V) and the target compound that are separated by chromatography. Alternatively, the mixture of the nucleosides (II) and (III) is debrominated by reaction with Bu3SnH and AIBN in refluxing toluene to give the same mixture of (V) and the target compound that is separated as before.