Synthesis of the anticodon hairpin (t)RNA(f)(Met) containing N-{[9-(beta-D-ribofuranosyl)-9H-purin-6-yl]carbamoyl}-L-threonine (=N-6-{{[(1S,2R)-1-carboxy-2-hydroxyropyl]amino}carbonyl}adenosine, t(6)A)

As part of our studies on the structure of yeast (t)RNA(f)(Met), we investi gated the incorporation of N-([9-(beta-D-ribofuranosyl) -9H-purin-6-yl] car bamoyl) -L-threonine (t(6)A) in the loop of a RNA 17-mer hairpin. The carbo xylic function of the L-threonine moiety of t6A was protected with a 2-(4-n itrophenyl)ethyl group, and a (tert-butyl)dimethylsilyl group was used for the protection of its secondary OH group. The 2'-OH function of the standar d ribonucleotide building blocks was protected with a [(triisopropylsilyl)o xy]methyl group. Removal of the base-labile protecting groups of the final RNA with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and then with MeNH2 was d one under carefully controlled conditions to prevent hydrolysis of the carb amate function, leading to loss of the L-threonine moiety.