10 wt of the substrate aldrich was added and the mixture was stirred at 160 u00b0 c in a sealed tube under d 2 atmosphere for 24 h after cooling to rt the reaction mixture was filtered using a membrane filter millipore millex u00ae u2014 lg the filtered catalyst was washed with boiling water 150 ml and the combined aqueous fractions were evaporated in vacuo and then again dissolved in h 2 o and evaporated 5 u00d7 25 ml to give 5 d deoxycytidine as a white solid 206 mg the structure of the nucleoside was confirmed by maldi tof voyager elite perseptive biosystems with hpa as a matrix found 228 225 45 mi 229 229 27 double deuterated product mi a suspension of 500 mg of 7 pd c catalyst prepared from pdcl 2 as described in chiriac et al 1999 42 377 385 in 8 ml of acetic acid d doac was stirred vigorously for 20 min in a deuterium atmosphere with intermittent bubbling of deuterium gas through the mixture 5 bromo 2 u2032 deoxycytidine 307 mg 1 mmol carbosynth uk converted into its benzoyl derivative using 3 equivalents of benzoyl chloride as described in m j gait oligonucleotide synthesis a practical approach irl press 1984 was added and the mixture was stirred vigorously for 5 h at room temperature under 1 atm pressure of d 2 and then filtered 410 mg 5 mmol.