Quinocarcin total synthesis

Two more complex examples of this reaction type are used in work on the total synthesis of quinocar-cin and gelsemine. A vinyl sulfide is employed as nucleophile in an Af-acyliminium cyclization to produce the bridged substructure of quinocarcin (equation 96).A genuine equivalent of the Mannich reaction is put to practice in a synthetic approach to gelsemine (equation 97). The iminium intermediate, simply generated by protonation of the enecarbamate, apparently reacts only with the enol shown in (128). 

D- and L-Threose derivatives have been utilized as chiral auxiliaries for asymmetric imine reductions in the total synthesis of quinocarcin 271 and 1-decarboxyquinocarcin 272 (Scheme 57) 119 7he methodology has also been applied to a range of model conqiounds. 20,121... 

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