Alkaloid from Grignard reagents

Weinreb and co-workers made use of a nucleophilic hyroxymethyl equivalent in the synthesis of the marine alkaloid lepadiformine.46 A highly stereoselective addition to a-methoxybenzamide 56 was achieved using the silylmethyl cuprate derived from Grignard reagent 57. Exposure of 58 to Fleming oxidation conditions provided 59 in high yield. 

The dihydropyridines resulting from analogous reactions of /V-acyl- or N-alkoxycarbonylpyridinium salts may be isolated and characterized moreover, they are valuable intermediates in elegant syntheses of alkaloids. What is more, the /V-alkoxycarbonylpyridinium salts may be generated in situ by the reaction of the pyridine with a chloroformate even in the presence of a Grignard reagent [9], An example is a four-step synthesis of ( )-lasubine II (Scheme 5.2), and a procedure is given for the key step [10]. 

The synthesis by Mattocks and Warren 161) ofsenecionine (CLXXXa) from retrorsine (CLXXXb) by oxidation with periodate to the keto ester, CLXXXIII, and reaction with the Grignard reagent has permitted the preparation of CH3-i C-senecionine for studies of the role of the total alkaloid in the plant and animal. 

Reduction of an alkylmercury halide or acetate with a borohydride provides an alternative method for accessing a carbon radical species (see Scheme 4.11). The alkylmercury compound can be prepared by one of a number of methods, such as from the corresponding Grignard reagent or from addition of Hg(OAc)2 to an alkene. For example, intramolecular amido-mercurafion of the alkene 50, followed by formation of the alkyl radical and addition to methyl acrylate provides a route to the alkaloid 8-coniceine (4.46). ... 

OTHER COMMENTS used as a solvent for waxes, oils, fats, gums, perfumes, and alkaloids an excellent solvent for nitrocellulose when mixed with alcohol useful in organic syntheses, especially as a reagent in Grignard and Wurtz type reactions used in the production of drugs of abuse, in the manufacture of gun powder, and as a primer for gasoline engines applications as an extractant of hormones, etc. from plant and animal tissues has also been used as an anesthetic. 

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