A number of other syntheses of coniine have been effected, of which that of Diels and Alder is of special interest. The initial adduct of pyridine and dimethyl acetylenedicarboxylate is tetramethylquinolizine-1,2,3,4-tetracarboxylate, which on oxidation with dilute nitric acid is converted into trimethyl indolizine-tricarboxylate. This, on hydrolysis and decarboxylation, furnishes indolizine, the octahydro-derivate of which, also known as octahydropyrrocoline is converted by the cyanogen bromide method successively into the bromocyanoamide, cyanoamide and "rac."-coniine. A synthesis of the alkaloid, starting from indolizine (pyrrocoline) is described by Ochiai and Tsuda.