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Abstract: An AE azabicyclic fragment, with a β-hydroxyl group at C-5 and a substituent at C-1, of the C19-diterpenoid alkaloids, was synthesized. The key reactions include an intramolecular Claisen-type condensation, double Mannich reaction, and stereoselective nucleophilic addition of carbonyl group with the assistance of steric effect of 1β-substituent. [Copyright &y& Elsevier]

Abstract: An tricyclic AEF fragment of C19-diterpenoid alkaloid bearing an angular methyl group and the oxygen function groups at C-1 and C-6 was successfully synthesized. The synthesis features a stereoselective intramolecular Diels–Alder reaction and a highly efficient intramolecular Mannich reaction as well as efficient functional groups transformations. [Copyright &y& Elsevier]

Abstract: A concise strategy for construction of B/C/D ring system of C19-diterpenoid alkaloids was described, which features a highly diastereoselective intramolecular Diels–Alder reaction of masked o-benzoquinone and an efficient Wagner–Meerwein 1,2-shift rearrangement. The functional group transformations of rearrangement product 19 demonstrate a potential for stereoselective installation of oxygen functions on D-ring of many type of C19-diterpenoid alkaloids. [Copyright &y& Elsevier]