Process for preparing amino acid esters useful as intermediates for compounds containing a fused bicyclic ring

A process for preparing a compound of the formula ##STR83## wherein m is zero or one and R.sub.3 is an acid protecting group which comprises:

• a) reacting a solution of diethylacetamido malonate with a base followed by reaction with a haloalkylacetate of the formula ##STR84## b) treating the product of part (a) with sodium hydroxide and heat and then acid and heat to give ##STR85## c) treating the product of part (b) with a hydrolyzing enzyme to give ##STR86## d) treating the product of part (c) to introduce the R.sub.3 group and give the desired product.