Of quinocarcin

Azomethine yhdes have also been subjected to reactions with 165 (Scheme 12.52). Gamer and Ho (288) developed the reaction of the photogenerated azomethine ylide 173 with 165 for the synthesis of quinocarcin. The reaction gave 174 with complete endo/exo selectivity and with more than 90% de. Other types of azomethine ylides have also been used in reactions with 165 and its derivatives (289,290). 

The synthetic utility of the photolytic decomposition pathway of pyrrolo[3,4-J]-1,2,3-triazole derivatives has been realised in the asymmetric synthesis of (—)-quinocarcin. Thus, the triazine (62) was irradiated using a mercury light source to give aziridine (63) in 90% yield via loss of nitrogen <93JA10742>. 

However, the synthesis of (—)-quinocarcin required a suitably substituted maleimide precursor which incorporated a chiral auxiliary moiety that could subsequently form part of the target molecule. Consequently, the maleimide (169) was reacted with methyl azide to give the triazoline (62) in 99% yield <93JA10742>. 

Katoh, T., Kirihara, M., Yoshino, T., Tamura, O., Ikeuchi, F., Nakatani, K., Matsuda, F., Yamada, K., Gomi, K., Ashizawa, T., Terashima, S. Synthetic studies on quinocarcin and its related compounds. 5. Synthesis and antitumor activity of various structural types of quinocarcin congeners. Tetrahedron 1994, 50, 6259-6270. 

Cytotoxic activities of quinocarcin derivatives (XXI) against HeLa cells were reported by Saito et aL (47). From their data Eq. 25 was obtained [33] ... 

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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