| Description |
A prototype multisubstrate analog of the glycinamide ribonucleo- tide formyltransferase (GAR Tfase) reaction would permit a more detailed study of the mechanism of formyl group transfer and allow for further determination of the parameters of enzyme binding and inhibition. The important structural features which could be modified in approaching a viable synthesis are discussed. The rationale for the types of structural modifications suggested, which include biological studies and their inferences are reviewed. The synthesis of diethyl N-2-isobutoxycarbonyl-5,8-dideaza folic acid, incorporating a novel carbamoyl blocking group has proven useful in the synthesis of a ureide-bridged intermediate towards a multisubstrate analog. The success of the N-2-isobutoxycarbonyl blocking group was limited to the dideazafolate class. Only the analog missing the pteridine portion of the analog, diethyl (N(2'3' -O-isopropylidene-(beta)-D-ribofuranos-1-yl)carbamoyl)methylureido - benzoylglutamate, was additionally approachable. Formation of an active acylation intermediate of the dideazafolate and phosgene allowed for the synthesis of the nucleoside, diethyl 2-isobutoxycarbonyl-5,8-dideaza-10-N((N(2'3'-O-isopropylidene-(beta)- D-ribofuranos-1-yl)carbamoyl)methyl)carbamoyl folic acid. Phospho- rylation of this nucleoside with a commercially available phosphoro- chloridate gave the pentultimate 5,8-dideaza multisubstrate analog. The characterization by proton NMR of the deblocked intermediates was successful through the tetraacid intermediate, 5,8-dideaza-10-N((N(2'3'-O-isopropylidene-(beta)-D-ribofuranos-1-yl) carbamoyl)methyl)carbamoyl folic acid-5'-phosphate. The difficul- ties toward this intermediate, as well as the results of application of several methods toward the fully deblocked intermediate are discussed. |
