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J Org Chem. 2013 Apr 19;78(8):3616-35. doi: 10.1021/jo400079z. Epub 2013 Apr 1.

Development of a large scale asymmetric synthesis of the glucocorticoid agonist BI 653048 BS H3PO4.

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Chemical Development, Boehringer Ingelheim Pharmaceuticals, Inc., 900 Old Ridgebury Road, P.O. Box 368, Ridgefield, Connecticut, 06877-0368, USA.


The development of a large scale synthesis of the glucocorticoid agonist BI 653048 BS H3PO4 (1·H3PO4) is presented. A key trifluoromethyl ketone intermediate 22 containing an N-(4-methoxyphenyl)ethyl amide was prepared by an enolization/bromine-magnesium exchange/electrophile trapping reaction. A nonselective propargylation of trifluoromethyl ketone 22 gave the desired diastereomer in 32% yield and with dr = 98:2 from a 1:1 diastereomeric mixture after crystallization. Subsequently, an asymmetric propargylation was developed which provided the desired diastereomer in 4:1 diastereoselectivity and 75% yield with dr = 99:1 after crystallization. The azaindole moiety was efficiently installed by a one-pot cross coupling/indolization reaction. An efficient deprotection of the 4-methoxyphenethyl group was developed using H3PO4/anisole to produce the anisole solvate of the API in high yield and purity. The final form, a phosphoric acid cocrystal, was produced in high yield and purity and with consistent control of particle size.

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