Solid phase synthesis of the 5'-half of the initiator t-RNA from B. subtilis.

Using cyanoethyldiisopropylamino phosphoramidite chemistry, four oligonucleotides constituting a part of the sequence of the initiator t-RNA from B. subtilis were synthesized. For the protection of the exocyclic amino functions of bases, phenoxyacetyl group was used for adenine and guanine, and acetyl group was preferred for cytosine. With these labile groups, final deprotection of the oligonucleotides can be performed in milder conditions, allowing the incorporation of 5,6-dihydrouridine in a 35-mer constituting the 5'-end of the t-RNA.