Pteridines. Part CXVIII

Abstract

Our approach to achieve a partial synthesis of methanopterin (1) started from 6-acetyl-O 4 -isopropyl-7-methylpterin (20) which was obtained either by condensation from 6-isopropoxypyrimidine-2,4,5triamine (19) and pentane-2,3,4-trione (6) or from 6-isopropoxy-5-nitrosopyrimidine-2,4-diamine (21) and pentane-2,4-dione (¼ acetylacetone; 22) (Scheme 2). NaBH 4 reduction of 20 led to 6-(1hydroxyethyl)-O 4 -isopropyl-7-methylpterin (23) which was converted into the corresponding 6-(1chloroethyl) and 6-(1-bromoethyl) derivatives 24 and 25. A series of nucleophilic displacement reactions in the side chain and at position 4 were performed as model reactions to give 26 -29, 32 -35, and 39 -41. Hydrolysis of the substituents at C(4) led to the corresponding pterin derivatives 30, 31, 36 -38, and 42. Analogously, 25 reacted with 1-(4-aminophenyl)-1-deoxy-2,3: 4,5-di-O-isopropylidene-d-ribitol (43), prepared from N-(4-bromophenyl)benzamide (47) via 49 and 50 to give 1-{4-{{1-[2-amino-7-methyl-4-(1methylethoxy)pteridin-6-yl]ethyl}amino}phenyl}-1-deoxy-d-ribitol (44) in 62% yield (Scheme 3). Acid cleavage of the isopropylidene groups at room temperature led to 45 and on boiling to 1-{4-{[1-(2-amino-3,4-dihydro-7-methyl-4-oxopteridin-6-yl)ethyl]amino}phenyl}-1-deoxy-d-ribitol (46). The next step, however, attachment of the ribofuranosyl moiety with 55 or 56 to the terminal 1-deoxy-d-ribitol OH group could not been achieved. The second component, bis(4-nitrobenzyl) 2-{[(2-cyanoethoxy)(diisopropylamino)phosphino]oxy}pentanedioate (61), to built-up methanopterin (1) was synthesized from 2hydroxypentanedioic acid (59) and worked well in another model reaction on phosphitylation with N 6benzoyl-2',3'-O-isopropylideneadenosine and oxidation to give 62 (Scheme 6).

Solvent Effects in Chemical Processes. Water-Assisted Proton Transfer Reaction of Pterin in Aqueous Environment

“…They have also reported the fluorescence, absorption spectra, and the effects of substituents and pH . For biological investigations, some pteridines have been synthesized and elucidated . NMR spectrum of 15 N was also used to characterize the dominant tautomer in the equilibrium in aqueous solution of quinonoid tetrahydropterin …”

Bicyclic 6-6 Systems: Pteridines

“…Other examples of side chain reaction include nucleophilic substitution reactions of pteridine 110 with primary amines in isopropylamine, which resulted in unexpected products. 80 Surprisingly, the isopropoxy group on C-4 was substituted by the amine, and the Cl-atom in the side chain of C-6 was replaced by the isopropoxy residue, giving products 112-114. When EtOH was used as solvent in the reaction between compound 110 and neopentylamine, this again resulted in alcohol substitution of the side chain to furnish 6-(1-ethoxyethyl)-7-methyl-N4-neopentylpteridine-2,4-diamine (115).…”

Continuum, discrete, and explicit solvation models for describing the low‐lying absorption spectrum of the pterin acid in aqueous environment

“…T here has been an increased interest in the photochemistry of the pterin molecule, mostly because of its important biological functions [1][2][3][4][5][6][7][8][9][10][11][12]. As such there is a considerable need to understand its properties in aqueous environment.…”