Convenient synthesis of 4,6-di-O-benzyl-myo-inositol and myo-inositol 1,3,5-orthoesters

Convenient high yielding methods for the preparation of 4,6-di-O-benzyl-myo-inositol, myo-inositol 1,3,5-orthoformate and myo-inositol 1,3,5-orthoacetate, without involving chromatography are described. Myo-inositol was converted to racemic 2,4-di-O-benzoyl-myo-inositol 1,3,5-orthoformate by successive treatment with triethyl orthoformate and benzoyl chloride. The dibenzoate obtained on benzylation with benzyl bromide and silver(I) oxide gave 2-O-benzoyl-4,6-di-O-benzyl-myo-inositol 1,3,5-orthoformate. Deprotection of the benzoate and the orthoformate with isobutylamine and aqueous trifluoroacetic acid, respectively gave 4,6-di-O-benzyl-myo-inositol in an overall yield of 67%. Myo-inositol orthoformate and orthoacetate were prepared and isolated as their tribenzoates. The free orthoesters were regenerated by deprotection of the benzoates by aminolysis with isobutylamine.