Stereospecific synthesis of oligonucleotides containing crotonaldehyde adducts of deoxyguanosine

Crotonaldehyde reacts with DNA to form two diastereomeric 1,N-2 cyclic addu cts of deoxyguanosine. A synthesis of the two diastereomeric deoxynucleosid es has been achieved by reaction of mixed diastereomers of 4-amino-1,2-pent anediol with 2-fluoro-O-6-(trimethylsilylethyl)-deoxyinosine. The resulting N-2-(1-methyl-3,4-dihydroxybutyl)-deoxyguanosine was treated with NaIO4, c leaving the vicinal diol to the aldehyde. Spontaneous cyclization gave the two diastereomers of the crotonaldehyde-adducted nucleoside that were readi ly separated by HPLC. The absolute configurations were assigned by an enant iospecific synthesis of one diastereomer from (S)-3-aminobutanoic acid. The synthetic strategy has been extended to preparation of a site-specifically adducted oligonucleotide by reaction of the mixed diastereomers of 4-amino -1,2-pentanediol with an 8-mer oligonucleotide containing 2-fluoro-O-6-(tri methylsilylethyl)-deoxyinosine. The diastereomeric oligonucleotides were se parated by HPLC and absolute configurations of the adducts were established by enzymatic digestion to the adducted nucleosides.