The alkylation of ethyl benzoylacetate (A) with beta-ethoxyethyl bromide (B) using potassium carbonate in dimethyl formamide at 80 C gives the beta-3-keto ester (I). Condensation of (I) with guanidine hydrochloride (C) using sodium methoxide in tert-butanol at 80 C gives the pyrimidine (II). Protection of the amino group is achieved by tormylation at room temperature with the mixed anhydride (III) from formic and acetic acids. Chlorination with an excess of phosphorus oxychloride at 100 C gives a mixture of (V) and (VIII). The mixture of chloropyrimidines (V, VIII) is stirred at room temperature with excess hydrazi-ne hydrate to give the aminohydrazinopyrimidine (VI). This is heated with ethyl orthoformate in triglyme at 135 C to give the bicyclic compound (VII). This triglyme solution is then heated to 20 C to effect a Dimroth type rearrangement to give SC-33643.