Succinic acid mono-[(2S,3R,6S,8R,9S)-3-butyl-8-[(2E,4E,8E)-(6S,7S)-6-(tert-butyl-dimethyl-silanyloxy)-9-carboxy-3,7-dimethyl-nona-2,4,8-trienyl]-2-((1E,3E)-4-carboxy-3-methyl-buta-1,3-dienyl)-9-methyl-1,7-dioxa-spiro[5.5]undec-3-yl] ester