Analogues of 2'(3')-O-L-phenylalanyladenosine as substrates and inhibitors of ribosomal peptidyltransferase.

The chemical syntheses of 2'(3')-O-(L-3-amino-3-phenylpropionyl)adenosine (2e), the corresponding D stereoisomer 2f, 2'(3')-O-(DL-phenylglycyl)adenosine (2g), 2'(3')-O-(N-benzylglycyl)adenosine (2h), and 9(2-O-L-phenylalanyl-beta-D-xylofuranosyl)adenine (3b) are described. Compounds 2e-h were obtained by acylation of 5'-O-(4-methoxytrityl)adenosine with the appropriate N-benzyloxycarbonyl or N-tert-butoxycarbonyl amino acids with dicyclohexylcarbodiimide in pyridine. The corresponding reaction of N-(benzyloxycarbonyl)-D-phenylglycine led to an almost complete racemization of the aminoacyl residue (compounds 2c and 2g). Subsequent chromatographic separation and deprotection of intermediates 2a-d afforded the desired target derivatives 2e-h. Product 3b was obtained by a similar acylation of 9-(3,5-O-isopropylidene-beta-D-xylofuranosyl)adenine with N-(benzyloxycarbonyl)-L-phenylalanine, followed by deblocking. The NMR spectra of 2' and 3' isomers of stereoisomers 2a and 2b are discussed. Compounds 2g and 3b are both substrates and inhibitors of Escherichia coli ribosomal peptidyltransferase, although the activity of 3b is low. Derivatives 2e,f,h do not accept AcPhe from N-AcPhe-tRNA in a peptidyltransferase-catalyzed reaction, but they inhibit the puromycin reaction in the same system. The order of inhibitory activity is 2e greater than 2f greater than 2h. The implications of these findings for the mechanism of peptidyltransferase and comparison of the latter with the action of chymotrypsin are discussed.