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Hydrophobic Vitamin B12 Derivatives: Unprecedented Formation of a 7-Membered Lactam



The synthesis of a new hydrophobic cobalamin derivative through intramolecular aminolysis is described. Under acidic conditions, (CN)2CobIII(10-NH2)7C1-ester formed a seven-membered lactam between the ester and amino groups present at the C8 and C10 positions. Subsequent Boc protection of the NH group enabled ring opening with primary amines, leading to derivatives functionalized at the C8 and C10 positions.