Full details of the synthesis of the fully elaborated aziridino[1,2-a]pyrrolidine substructure 2 of the antitumor agents azinomycins A and B are reported. Stereoselective bromination of dehydroamino acid 4 provided control of olefin configuration in the final product, as a consequence of a stereospecific cyclization of aziridine 3 onto the proximal beta-bromoacrylate, which effected pyrrolidine ring introduction. Dehydroamino acid 4 was constructed by olefination of aldehyde 5 with a glycine-based phosphonate. Two complementary synthetic routes to 2 are presented. In the first route, the selectively protected C12/C13 diol system of the targets was introduced into starting structure 6 in a stereocontrolled manner using Brown's (gamma-alkoxyallyl)-diisopinocampheylborane reagent system. Transient protection of the C12 hydroxyl group of 48 as the trimethylsilyl ether was used to prevent C13 acetate migration prior to cyclization. Deprotection of the C12 hydroxyl following cyclization to the azabicyclic system afforded the extremely unstable core substructure 41, which could not be isolated, but was characterized in situ. In the second route, the racemic gamma-alkoxystannane 8 was added in a chelation-controlled manner to serinal derivative 9 under conditions of kinetic resolution for introduction of the C12 and C13 stereogenic centers of the target. Phenylacetate and methoxyacetate esters were used for C12 hydroxyl protection. This work represents the first synthesis of the intact core substructure 44 of this novel class of natural products.