Process and intermediates for the preparation of spiro[isoquinoline-4(1H),3-pyrrolidine]1,2,3,5 (2H)-tetrones which are useful as aldose reductase inhibitors

Granted: Dec 8, 1992 Filed: Jan 2, 1992

This patent predates the USPTO's electronic file wrapper — prosecution documents from this era exist only in the Patent Office's paper records. A certified copy of the file history can be ordered from the USPTO's paper archives.