Esterification Diazomethane-Alumina

Other important porphyrins which can be derived from hemin are hematoporphyrin (5) and mesoporphyrin (6). Hematoporphyrin (5) which is commercially available at a relatively low price is sensitive towards acid due to the 1-hydroxyethyl groups, so commercial samples contain only 60 to 70% of hematoporphyrin. Pure hematoporphyrin dimethyl ester which is a racemic and diastereomeric mixture of four stereoisomers can be obtained by esterification with diazomethane and subsequent chromatography on neutral alumina.84 The pure stereoisomers can be prepared by enantioselective reduction of diacetyldeuteroporphyrin dimethyl ester.85a b The... 

Monoesterification of dicarboxylic acids. Chemiabsorption of a dicarboxylic acid on alumina or silica can be used to effect selective esterification of one acid group with diazomethane. The method was demonstrated by conversion of terephthalic acid, C6H4-l,4-(COOH)2) into the monomethyl ester in quantitative yield. 

Methyl O-methyl-7-ketopodocarpate (324) was reduced with sodium boro-hydride to the hydroxyester 325. Birch reduction of 325 followed by acidic hydrolysis and esterification with diazomethane afforded the dienone 326. Reduction of 326 with sodium borohydride followed by acetylation and treatment of the epimeric mixture with m-chloroperbenzoic acid afforded 327. The latter was rearranged with BF3 in ether to yield the ketone 328 which on chromatography over alumina gave the dienone 329. Reaction of 329 with maleic anhydride in refluxing toluene followed by esterification... 

Esterification Alumina. Boron trifluoride. Diazomethane. Dimethylformamide dimethyl acetal. Dimethylformamide dineopentyl acetal. Dimethyl sulfite. Diphenyidiazomethane. Ethyldicyclohexylamine. Ion-exchange resins. Isobutene. Methanesulfonic anhydride. 3 % Methanolic HCl (see Acetyl chloride). Methyl iodide. l-Methyl-3-p-tolyltriazine. Poly-phosphoric acid. Sulfosalicylic acid. Sulfuryl chloride. p-Toluenesulfonic acid. p-Tpluene-sulfonyl chloride. Triethylamine. Triethylorthoformate. Trifluoroacetic anhydride. Esterification of phosphoric acid Trichloroacetonitrile. 

---