L-tartaric acid is preferred. maleic acid can be used also, if it can not be bought it can be made by partial decomopsition of fumaric acid. when fumaric acid is heated (preferably under nitrogen or CO2) to close to its decomp temp it sublimes into maleic anhydride. ill have to dig up my epimerization workup that lets you take the ISO-LSA (still in the non polar mother liquor) and convert (partially, 80%) into active LSA to increase yield.