| abstract |
The present invention provides method for making a compound of formula (1) comprising the steps of reacting compounds of formulas (2) and (3) to produce a compound of formula (4) wherein R1, R2, R3, R4 and R5 are defined as described herein. The compound of formula (4) is then converted to the compound of formula (1). The invention further comprises compounds of formula (3) and (4) and methods for making compounds of formulae (3) and (4). |