Concise synthesis of the bicyclic core of the chromoprotein antibiotics kedarcidin and neocarzinostatin by transannular reductive cyclization of a tetrayne precursor

Article abstract of DOI:10.1016/S0040-4039(98)02279-5

The oxygenated [7.3.0]-bicyclododecadienediyne 8 is synthesized in 9 steps from L,-dimethyl tartrate. In the key transformation, transannular reductive cyclizalion of the potassium salt of the tetrayne alcohol 7 with NaAIH(OCH₂CH₂(NCH₃)₂) affords the bicyclic product 8 in 50-54% yield. This sequence provides a rapid entry into the strained bicyclic core structures of kedarcidin and neocarzinostatin chromophores (1 and 2, respectively).