AN IMPROVED SYNTHESIS OF 1-(2-DEOXY-BETA-D-ERYTHRO-PENTOFURANOSYL)QUINAZOLINE-2,4(3H)-DIONE AND ITS INCORPORATION INTO G-RICH TRIPLE-HELIX FORMING OLIGONUCLEOTIDES

A convenient synthesis of 1-(2-deoxy-beta-D-erythro-pentofuranosyl)quinazoline-2,4(3H)-dione (6) has been accomplished. The structural conformation of (6) was derived by 2D NMR, COSY and NOESY experiments. Nucleoside (6) was incorporated into G-rich tripler forming oligonucleotides (TFOs) by solid-support, phosphoramidite method. The tripler forming capabilities of modified TFOs (S2, S3 and S4) has been evaluated in antiparallel motif with a target duplex (duplex-31) 5'd(GTCACTGGCCCTTCCTCCTTCCCGGTCTCAG)3'-5'd(CAGTGACCGGGAAGGAGGAAGGGCCAGAGTC)3' (D1) at pH 7.6. The parallel tripler formation of a shorter TFO (S6) containing Q has also been studied with a target duplex-11 (D2) at PH 5.0.