New Efficient Synthesis of tRNA Related Adenosines Bearing the Hydantoin Ring (ct A, ms ct A) by Intramolecular Cyclization of N -(N-Boc-α-aminoacyl)-adenosine Derivatives.

A novel and efficient way for the synthesis of N -hydantoin-modified adenosines, which utilizes readily available N -(N-Boc-α-aminoacyl)-adenosine derivatives, was developed. The procedure is based on the epimerization-free, Tf O-mediated conversion of the Boc group into an isocyanate moiety, followed by intramolecular cyclization. Using this method two recently discovered hydantoin modified tRNA adenosines, that is, cyclic N -threonylcarbamoyl-adenosine (ct A) and 2-methylthio-N -threonylcarbamoyladenosine (ms ct A) were prepared in good yields.