So why do we need to be offering two chemical phosphorylation reagents? The original chemical phosphorylation reagent (CPR) (10-1900) works wonderfully giving the 5'-phosphate in virtually quantitative yield. Unfortunately though, it is not compatible with DMT-on purification techniques since the sulfonylethyl group is eliminated in ammonium hydroxide regardless of the presence of the DMT group. Enter CPR II. Coupling efficiency with CPR II (10-1901) is exactly the same as with the original version. However, now you have a choice. Remove the DMT group on the synthesizer and the ammonium hydroxide step generates the 5'-phosphate. Or now you can leave the DMT on and simply purify the oligo using a reverse phase cartridge or HPLC. We are happy to report that CPR II has been awarded US Patent No. 5,959,090 which issued on September 28, 1999.