Abstract

A new convergent synthetic procedure has been developed for preparation of lariat heptaribonucleotide 19, modelling the lariat formed in Group II and nuclear pre-mRNA processing reaction (Splicing). The first three steps in this strategy involves the condensation of the appropriately protected 5'-O-levulinylated-cytidylyl(3' --> 5')uridine-3'-phosphodiester 4 with the 3, 5'-dihydroxy-6-N-(4-anisoyl)-2'-O-pixyl(9-phenylxanthen-9-yl)adenosine 14, in presence of an activating agent, to give 15a (49%). Chemospecific phosphorylation of 3'-OH of 15a afforded the intermediate 15b (92%) which was treated with mild acid to achieve a regio specific removal of the 2'-O-pixyl group to give 15c (91%). The fourth step is the introduction of the (2-cyanoethyl)-(2-(4-nitrophenyl)ethyl)phosphotriester moiety to the 2'-OH of the branch-point adenosine in 15c in a single step, by using (2-cyanoethoxy)-(2-(4-nitrophenyl)ethoxy)-(diisopropylamino)phosphine, to give the crucial branch-point building block 15d (58%) with two dissimilar vicinal phosphates at 2'- and 3- of the branch-point. 15d was then condensed with the appropriately protected 5'-hydroxy-uridylyl (3' --> 5')-(2',3'-di-O-acetylcytidine) 11 to afford the fully protected intermediate 16a (57%). Regiospecific deblocking of 2-cyanoethyl group froth 16a afforded the 2'-(2-(4-nitrophenyl)ethylphosphodiester 16b (94%), which was condensed with the dimeric 5'-hydroxyguaninylyl(3' --> 5')uridine-3'phosphotriester 13 to afford the fully protected 17a (59%). The 5'-O-levulinyl and the 2-cyanoethyl groups were regiospecifically removed from 17a successively to afford first 17b (88%) and then the 5'-hydroxy-3'-phosphodiester block 17c (68%). 17c was allowed to undergo intramolecular phosphorylation, in presence of an activating agent, under a condition of high dilution to afford the fully protected lariat-RNA 18 (66%) which was then deprotected in four steps and purified to give the fully deprotected lariat-RNA 19 (29%). Detailed 500 MHz H-1-NMR and 202.4 MHz P-31-NMR studies, using Clean-TOCSY, DQF-COSY, NOESY & P-31-H-1-NMR shift correlation techniques, have unequivocally established the purity and the structural integrity of lariat 19.

Published in

Tetrahedron
1993, Volume: 49, number: 3, pages: 649-668
Publisher: PERGAMON-ELSEVIER SCIENCE LTD

UKÄ Subject classification

Organic Chemistry


Publication identifier

DOI: https://doi.org/10.1016/S0040-4020(01)86267-0

Permanent link to this page (URI)

https://res.slu.se/id/publ/83896