Pteridines CV

Abstract

Summary Treatment of L-biopterin (I) with N,N-dimethyformamide dimethyl- (or diethyl)acetal and then with acetic anhydride in pyridine gave 1',2'-di-O-acetyl-N'-(N,N-dimethylaminomethylene)-L-biopterin (4), which was converted by the Mitsunobu reaction into 3-methyl (5) and 3-p-nitrophenetyl derivatives (7). The protective groups on the side chain diols and N2 of these compounds were selectively cleaved to furnish products 6, 8-10, among which 9 is naturally occurring 3-methyl-L-biopterin and 8 is N',N(3)-protected biopterin, a versatile intermediate for various reactions on the side-chain diol. In contrast, the same Mitsunobu reactions of tri-N2:I',2'-0-acetyl-L-biopterin (II) afforded 04-methyl (12) and 04-NPE derivatives (13), both of which yielded 0 4-methyl-L-biopterin (14) and subsequently led to 4-amino-L-biopterin (18).

Synthetic studies on pterin glycosides: the first synthesis of 2′-O-(α-d-glucopyranosyl)biopterin

“…17 A rational consideration of the available conditions to remove the protecting groups of the glycoside derived from 9 led us to employ p-methoxybenzyl (PMB) group for protection of 1'-hydroxy, N,N-dimethylaminomethylene group for 2-amino, and 2-(4-nitrophenyl)ethyl (NPE) group for N-3 of the ring. 18 …”

“…Removal of the protecting groups of 24 was performed by the following 4-step-procedures: first, cleavage of PMB by use of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) to afford 6 in 88%, then the three successive treatment with sodium methoxide (to cleave benzoyl groups), aqueous ammonia (to cleave the N,N-dimethylaminomethylene group), and DBU (to cleave the NPE group) 18 furnished 2'-O-(β-D-glucopyranosyl)biopterin (2b), the anomeric isomer of the natural product, in 89% overall yield from 6. Structure of 2b was unambiguously established as the corresponding hexaacetyl derivative 25b obtained by usual acetylation.…”

Pteridines Part CXXI: Protection of (6R)-5,6,7,8-Tetrahydro-L-biopterin

“…In contrast to the alkylation of N 2 -acetylpterin [5] or N 2 ,1 0 ,2 0triacetyl-L-bioterin [12] that led to the corresponding O 4 -alkyl derivatives, we believe that the 5-acetyl group in the 5,6,7,8tetrahydropteridine series sterically hinders Mitsunobu alkylation at the peri-position.…”

First synthesis of asperopterin A, an isoxanthopterin glycoside from Aspergillus oryzae

“…Mitsunobu reaction of 14 with p -nitrophenylethyl (NPE) alcohol in the presence of triphenylphosphine and diisopropyl azodicarboxylate (DIAD) in THF yielded the N(3)-NPE derivative ( 15 ) [21], which was then treated with tetrabutylammonium fluoride to provide 6-hydroxymethyl compound ( 16 ), the key precursor for glycosylation. Thus, an improved synthesis of the 6-hydroxymethyl-7-xanthopterin derivative from 5 was accomplished in an appreciably better yield, compared with the reported routes shown in Scheme 1 .…”