.beta.-Phenylalanine, N-benzoyl-2-[[(2-carboxyethyl) carbonyl]oxy]-, 6,12b-diacetoxy-12-(benzoyloxy)- 2a,3,3a,4,5,6,9,10,11,12,12a,12b-dodecahydro-4,11- dihydroxy-4a,8,13,13-tetramethyl-5-oxo-7,11-methano- 1H-cyclodeca[3,4]benz[1,2-b]oxet-9-yl ester, sodium salt NSC600221