US 7,485,726 B2
Process for the preparation of risedronate sodium hemi-pentahydrate
Srinivasa Rao V. N Divvela, Hyderabad (India); Lenin Racha, Hyderabad (India); Sivakumaran Meenakshisunderam, Hyderabad (India); and Ramesh Dandala, Hyderabad (India)
Assigned to Aurobindo Pharma Ltd., Hyderabad (India)
Filed on Jan. 16, 2007, as Appl. No. 11/653,556.
Claims priority of application No. 94/2006 (IN), filed on Jan. 20, 2006.
Prior Publication US 2007/0173484 A1, Jul. 26, 2007
Int. Cl. C07F 9/38 (2006.01); C07D 213/30 (2006.01)
U.S. Cl. 546—22 19 Claims
 
1. A process for the selective preparation of 3-pyridyl-1-hydroxyethylidene-1,1-bisphosphonic acid sodium in hemi-pentahydrate form of Formula (I),

OG Complex Work Unit Drawing
which comprises treating a compound of Formula III,

OG Complex Work Unit Drawing
wherein M+ represents organic amine base with a base capable of giving sodium ions in a mixture of water and solvent to produce 3-pyridyl-1-hydroxyethylidene-1,1-bisphosphonic acid sodium hemipentahydrate of Formula (I).