合成路线1

The synthesis of penciclovir by two related ways has been reported: 1) The reaction of 2-(hydroxymethyl)butane-1,4-diol (I) with formaldehyde (or an aldehyde such as trimethylacetaldehyde) (II) by means of H2SO4 (or p-toluenesulfonic acid, TsOH) gives the dioxane (III), which by reaction first with methanesulfonyl chloride and triethylamine and then with NaI in acetone affords the corresponding 5-(2-iodoethyl)-1,3-dioxane (IV). The reaction of (IV) with 2-amino-6-chloropurine (V) by means of K2CO3 in DMF gives the corresponding condensation product (VI), which is finally hydrolyzed and deprotected with refluxing 2M aqueous HCl. 2) The reaction of triol (I) with 2,2-dimethoxypropane (VII) by means of TsOH gives the corresponding 1,3-dioxane (VIII), which by reaction with triphenylphosphine and CBr4 is converted to the 5-(2-bromoethyl) derivative (IX). The reaction of (IX) with the purine (V) by means of K2CO3 as before affords the corresponding condensation product (X), which is hydrolyzed and deprotected with 2M HCl as before.