2,20-cycloaspidospermidine-3-carboxylic acid, 6,7-didehydro-, methyl ester InChI=1/C21H24N2O2/c1-13-19-8-5-10-23-11-9-20(18(19)23)14-6-3-4-7-16(14)22-21(13,20)15(12-19)17(24)25-2/h3-8,13,15,18,22H,9-12H2,1-2H methyl 6,7-didehydro-2,20-cycloaspidospermidine-3-carboxylate