(SP-4-2-(7R-(3(2E,7R*,11R*))))-(3,7,11,15- tetramethyl-2-hexadecenyl 3,4-didehydro-9,14-diethenyl-21-(methoxycarbonyl)-4,8,13,18-tetra methyl-20-oxo-3-phorbinepropanoato(2-)-N(23),N(24), N(25),N(26))magnesium