- Enantioselective synthesis of brinzolamide (AL-4862), a new topical carbonic anhydrase inhibitor. The "DCAT Route" to thiophenesulfonamides
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A large scale synthesis of the topical carbonic anhydrase inhibitors AL-4623A (13a-HCl) and AL-4862 (13b) from 3-acetyl-2,5-dichlorothiophene ("DCAT", 1) is described. Reaction of 1 with NaSBn gave thioether 2, which was converted via sulfenyl chloride 3 and sulfenamide 5 to sulfonamide 6. Bromination of 6 gave bromo ketone 7, which upon reduction with (+)-B-chlorodiisopinocampheylborane and cyclization of the resulting bromohydrin produced S thieno[3,2-e]-1,2-thiazine 8a (96% ee) after chromatography. Treatment of 8a in THF with -BuLi at -70 °C resulted in Li-Cl exchange. Reaction of the thienyllithium with SO2 and hydroxylamine O-sulfonic acid afforded bis-sulfonamide 11a. Protection of lia as the acetimidate 12a, followed by tosylation and animation, gave R amine 13a. The synthesis of 13b proceeded via primary sulfonamide 16, which was brominated, reduced, and cyclized to give S thieno[3,2-e]-1,2-thiazine 18 (>98% ee). By virtue of the ionizable NH, 18 was separable from reduction byproducts by base extraction. Alkylation of 18 with 3-bromopropyl methyl ether afforded 8b, which was converted as above, via lib, to AL-4862 (13b). These procedures provided multihundred gram lots of 13a and 13b.
- Conrow, Raymond E.,Dean, W. Dennis,Zinke, Paul W.,Deason, Michael E.,Sproull, Steven J.,Dantanarayana, Anura P.,DuPriest, Mark T.
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p. 114 - 120
(2013/09/08)
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