and 5 pd c 100 mg added a balloon filled with hydrogen was placed on top of the reaction vessel after 6 hours at 23 u00b0 c tlc showed the absence of starting material the reaction mixture was filtered through a 0 45 micron nylon membrane to remove the catalyst and the solvent was removed to afford the desired product as a white solid 350 mg 99 which was identical spectral and analytical data to example 16 r 9 4 l valyloxy 2 l valyloxymethyl butyl guanine from example 23 step b 100 mg 0 126 mmole was dissolved in 0 1 n naoh aqueous solution 6 3 ml 0 63 mmole at room temperature at intervals an aliquot was taken and neutralized with 0 5 n trifluoroacetic acid the aliquots were evaporated and analyzed by hplc to monitor the progress of the reaction after 4 hours 0 5 n trifluoroacetic acid solution 1 26 ml 0 63 mmole was added to the solution and the reaction mixture was evaporated the desired product was purified by hplc ymc 50 u00d7 4 6 mm gradient 0 1 tfa 0 50 0 1 tfa in acetonitrile in 20 minutes uv detection at 254 nm yield 13 6 1 h nmr d 2 o u03b4 8 81 s 1h 4 36 m 4h 4 01 d 1h 3 74 m 2h 2 64 m 1h 2 25 m 1h 1 73 m 2h 1 03 dd 6h hplc separation of the reaction solution from example 27 gave the titled compound in 29 2 yield 1 h nmr dmso d 6 u03b4 8 38 s 3h 8.