The synthesis of the 5′-monomethoxytrityl-2′-tert-butyldimethylsilyl-3′-levulinylribonucleosides 4 of the four major bases involved in the phosphite procedure for the synthesis of oligoribonucleotides is described along with the 2′,3′-isomeric derivatives 6. This report describes a total protection system for nucleotide units which allows for the block condensation procedure to be used for the synthesis of long chains. The procedure is illustrated by the synthesis of a hexadecauridylic acid.

A series of phosphorodichloridites bas been prepared incorporating the most commonly used phosphate protecting groups in oligonucleotide synthesis. The groups include trichloroethyl, tribromoethyl, cyanoethyl, benzyl, methyl, p-chlorophenyl, and nitrophenethyl. The trichloroethyl and the nitrophenethyl appear to be the most stable groups while the cyanoethyl and methyl offer specific advantages. The benzyl and p-chlorophenyl groups are subject to limitations on their utility. Condensations can be carried out in a range of solvents including THF, pyridine, and DMF and at temperatures from −78 °C to 20 °C with a slight drop in yield with increasing temperature, at least for dinucleotide condensations.

No abstract

Positive and negative secondary Ion mass spectra have been measured for eight fully protected diribonucleoside monophosphates with various permutations of bases and protecting groups. The spectra, produced by 8-28 keV Cs+ Ions, were examined In a tlme-of-fllght mass spectrometer. The spectra yield a wealth of diagnostically useful Information enabling determination of the molecular weight, Identification of the protecting groups present, Identification of the nucleobases present, and determination of the base sequence. Many of the Ions are metastable (lifetimes ~10 ps or less). Preliminary studies on a protected trlribonucleoside diphosphate confirm that the technique can be extended to molecules with molecular mass up to at least 2100.

No abstract