The invention relates to a method for totally synthesizing a
natural product (+ / -)-rupestine G and resolving enantiomers. The method comprises the following steps: oxidizing the
raw material 2-methyl-5-bromopyridine (1) by m-chloroperoxybenzoic acid to obtain a
nitrogen oxidation product compound 2, carrying out a Reissert-Henze reaction to perform cyano substitution so as to obtain a compound 3, carrying out a
decarboxylation reaction on the compound 3 and
potassium monoethyl malonate to obtain beta-ketoester 4, carrying out
alkylation under the condition of
sodium ethylate to obtain a compound 5, carrying out a
coupling reaction to obtain a compound 6, carrying out an intramolecular olefin double replacement reaction on the compound 6 to obtain a key intermediate compound 7, carrying out reduction with
sodium borohydride to obtain a compound 8, carrying out a reaction under the condition of
pyridine / MsCl to obtain a compound 9, hydrolyzing the compound 9 under the action of
lithium hydroxide, carrying out methyl esterification by using iodomethane to obtain a compound 10, carrying out
palladium-carbon
catalytic hydrogenation to obtain a pair of diastereoisomers 11 and 12, and carrying out resolution by a semi-preparative high performance liquid chromatograph to obtain the
natural product rupestine G and three stereoisomers, namely a compound 13, a compound 14 and a compound 15.