The active extract of the seeds of Brucea jauanica has yielded bruceoside-A (1) and -B (2), two novel potent antileukemic quassinoid glycosides of bruceosin (15) and brusatol (8), respectively, as well as brucein-D (3) and -E (4).The structure and stereochemistry of these compounds have been established from chemical transformation, correlations, and spectral analyses.A three-step sequential procedure has been developed whereby a "one-pot'' reduction of aromatic ester groups directly to methyl is now possible. One of these steps involves conversion of the aromatic ester to a trimethylsilyloxy
Pyridinium ethoxycarbonyl-(3-oxocyclohexen-l -yl)methylides (VI1)-(IX) and 3.3-diacyl-1 -ethoxycarbonytallylides (X)-(XIII) are prepared by the reaction of 1 -ethoxycarbonylmethylpyridinium bromides (111) and (IV) with 3-chlorocyclohex-2-enones and 3-ethoxymethylenepentane-2.4-dione or diethyl ethoxymethylenernalonate, respectively. Refluxing the ylides (VI1)-(IX) in xylene affords the ethyl 10-oxo-7.8,g.l O-tetrahydro-pyridoE2.1 -a]isoindole-6-carboxylates (XV1)-(XVIII), and the ylides (X) and (XII) give diethyi indolitine-1.3-dicarboxylate (XIX) and ethyl 1 -acetylindolitine-3-carboxylate (XX), respectively. However, simllar treatment of the ylides (XI) and (XIII) affords ethyl indolizine-3-carboxylate (XXVII) and the keto-ester :XX), respectively. The mechanisms for the formation of the indolizine derivatives are discussed.
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