Fig. 6: Total synthesis of (-)-cepharamine ( 4). | Nature Communications

Fig. 6: Total synthesis of (-)-cepharamine ( 4).

From: Unified divergent strategy towards the total synthesis of the three sub-classes of hasubanan alkaloids

Fig. 6

Reagents and conditions: (a) TMSOTf (3.0 equiv), 2,6-lutidine (5.0 equiv), DCM, 0 °C to rt, then TBAF (3.0 equiv), 0 °C, 77%; (b) KOtBu (2.0 equiv), Et2O/HCO2Et = 10/1, 0 °C to rt, then trimethylene dithiotosylate (1.0 equiv), AcOK (10.0 equiv), MeOH, reflux, 62%; (c) KOtBu (3.0 equiv), Me2SO4 (1.1 equiv), DMSO, rt, 85%; (d) PIFA (2.5 equiv), TFA (2.0 equiv), MeCN/H2O = 1/1, then TFA, rt, 91%. TMSOTf trimethylsilyl trifluoromethanesulfonate, TBAF tetra-n-butylammonium fluoride, DMSO dimethyl sulfoxide, PIFA [bis(trifluoroacetoxy)iodo]benzene.

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