Peters, Rene published the artcilePractical Formal Total Syntheses of the Homocamptothecin Derivative and Anticancer Agent Diflomotecan via Asymmetric Acetate Aldol Additions to Pyridine Ketone Substrates, Application of 2-Chloroisonicotinic acid, the publication is Journal of Organic Chemistry (2006), 71(20), 7583-7595, database is CAplus and MEDLINE.
Two practical, efficient, and scalable asym. routes to DE ring fragment I, a key building block in the synthesis of the homocamptothecin derivative diflomotecan (II), are described. The “acetal route” starts from 2-chloro-4-cyanopyridine and represents an enantioselective and optimized modification of the original racemic discovery chem. synthesis. The inefficient optical resolution procedure was replaced by an efficient asym. acetate aldol addition (dr 87:13) to a ketone substrate as the key step generating the (R)-configured quaternary stereocenter with high stereoselectivity. I was finally obtained in 8.9% overall yield (er 99.95:0.05) over nine steps, avoiding chromatog. purifications and comparing favorably with the initial procedure. In the related “amide route” starting from 2-chloroisonicotinic acid, a secondary amide directing group was used to facilitate the ortho lithiation of the pyridine 3-position. The key step of this protocol again consists of a practical asym. acetate aldol addition (dr = 87:13). The DE ring building block I was thus obtained in 11.1% overall yield (er > 99.95:0.05) over nine steps requiring only one chromatog. purification
Journal of Organic Chemistry published new progress about 6313-54-8. 6313-54-8 belongs to chlorides-buliding-blocks, auxiliary class Pyridine,Chloride,Carboxylic acid, name is 2-Chloroisonicotinic acid, and the molecular formula is C6H4ClNO2, Application of 2-Chloroisonicotinic acid.
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