MetaboLights
A fumiquinazoline that consists of imidazoindole and pyrazinoquinazoline units connected by a methylene group.
Identification
(1S,4R)-4-{[(2S,9S,9aS)-9-hydroxy-2-methyl-3-oxo-2,3,9,9a-tetrahydro-1H-imidazo[1,2-a]indol-9-yl]methyl}-1-methyl-2H-pyrazino[2,1-b]quinazoline-3,6(1H,4H)-dione
Species
Europe PubMed Central results
Total synthesis of the fumiquinazoline alkaloids: solid-phase studies.
Author: Wang H, Ganesan A.
Abstract: We have previously described an efficient four-step synthesis of the fumiquinazoline alkaloids (Wang, H.; Ganesan, A. J. Org. Chem. 1998, 63, 2432-2433). Here, we demonstrate that this route is readily adaptable to combinatorial synthesis on solid phase. Linear tripeptides containing a central anthranilate unit were assembled on the Wang resin and subjected to dehydration and cyclative release to yield the pyrazino[2,1-b]quinazoline-3,6-diones in high purity. To demonstrate the scope of this protocol, a small library [ca. 20 compounds] of unnatural analogues was prepared by parallel synthesis.
DOI: 10.1021/cc9900807
Total synthesis of the fumiquinazoline alkaloids: solution-phase studies.
Author: Wang H, Ganesan A.
Abstract: Biomimetic total syntheses of glyantrypine, fumiquinazoline F, fumiquinazoline G, and fiscalin B were achieved in four steps from tryptophan methyl ester. In the key step, the anthranilamide residue in a linear tripeptide is dehydrated to a benzoxazine by reaction with triphenylphosphine, iodine, and a tertiary amine. The benzoxazines subsequently undergo rearrangement to the natural products via an amidine intermediate. This dehydrative oxazine to quinazoline route is applicable to a broad range of N-acylanthranilamides, including sterically hindered cases.
DOI: 10.1021/jo9914364
Total synthesis of (-)-fumiquinazolines A, B, C, E, H, and I. Approaches to the synthesis of fiscalin A.
Author: Snider BB, Zeng H.
Abstract: The first syntheses of (-)-fumiquinazolines A, B, and I, which proceed in 14 steps from protected tryptophan, anthranilic acid, leucine, and alanine in 7% overall yield, are described. Tricycle 30 was formed by a palladium-catalyzed cyclization. Oxidation of 30a with saccharine-derived oxaziridine 21 for fumiquinazolines A and B and oxidation of 30b with dimethyldioxirane for fumiquinazoline I selectively formed the appropriate imidazoindolone stereoisomers. Application of the Ganesan-Mazurkiewicz cyclization completed the syntheses. Efficient 14-step syntheses of (-)-fumiquinazolines C (7) and E (3) and a 15-step synthesis of (-)-fumiquinazoline H (8) using FmocNHCH(CH2SePh)CO2H as a dehydroalanine precursor that spontaneously eliminated benzeneselenol without oxidation under the cyclization conditions are also reported. Model 86 for fiscalins A with the H and OH anti to each other has been prepared, but the procedure that worked for the model failed with the fully functionalized side chain.
DOI: 10.1021/jo0264980
Enzymatic processing of fumiquinazoline F: a tandem oxidative-acylation strategy for the generation of multicyclic scaffolds in fungal indole alkaloid biosynthesis.
Author: Ames BD, Liu X, Walsh CT.
Abstract: Aspergillus fumigatus Af293 is a known producer of quinazoline natural products, including the antitumor fumiquinazolines, of which the simplest member is fumiquinazoline F (FQF) with a 6-6-6 tricyclic core derived from anthranilic acid, tryptophan, and alanine. FQF is the proposed biological precursor to fumiquinazoline A (FQA) in which the pendant indole side chain has been modified via oxidative coupling of an additional molecule of alanine, yielding a fused 6-5-5 imidazoindolone. We recently identified fungal anthranilate-activating nonribosomal peptide synthetase (NRPS) domains through bioinformatics approaches. One domain previously identified is part of the trimodular NRPS Af12080, which we predict is responsible for FQF formation. We now show that two adjacent A. fumigatus ORFs, a monomodular NRPS Af12050 and a flavoprotein Af12060, are necessary and sufficient to convert FQF to FQA. Af12060 oxidizes the 2',3'-double bond of the indole side chain of FQF, and the three-domain NRPS Af12050 activates l-Ala as the adenylate, installs it as the pantetheinyl thioester on its carrier protein domain, and acylates the oxidized indole for subsequent intramolecular cyclization to create the 6-5-5 imidazolindolone of FQA. This work provides experimental validation of the fumiquinazoline biosynthetic cluster of A. fumigatus Af293 and describes an oxidative annulation biosynthetic strategy likely shared among several classes of polycyclic fungal alkaloids.
DOI: 10.1021/bi1012029
Complexity generation in fungal peptidyl alkaloid biosynthesis: oxidation of fumiquinazoline A to the heptacyclic hemiaminal fumiquinazoline C by the flavoenzyme Af12070 from Aspergillus fumigatus.
Author: Ames BD, Haynes SW, Gao X, Evans BS, Kelleher NL, Tang Y, Walsh CT.
Abstract: The human pathogen Aspergillus fumigatus makes a series of fumiquinazoline (FQ) peptidyl alkaloids of increasing scaffold complexity using L-Trp, 2 equiv of L-Ala, and the non-proteinogenic amino acid anthranilate as building blocks. The FQ gene cluster encodes two non-ribosomal peptide synthetases (NRPS) and two flavoproteins. The trimodular NRPS Af12080 assembles FQF (the first level of complexity) while the next two enzymes, Af12060 and Af12050, act in tandem in an oxidative annulation sequence to couple alanine to the indole side chain of FQF to yield the imidazolindolone-containing FQA. In this study we show that the fourth enzyme, the monocovalent flavoprotein Af12070, introduces a third layer of scaffold complexity by converting FQA to the spirohemiaminal FQC, presumably by catalyzing the formation of a transient imine within the pyrazinone ring (and therefore acting in an unprecedented manner as an FAD-dependent amide oxidase). FQC subsequently converts nonenzymatically to the known cyclic aminal FQD. We also investigated the effect of substrate structure on Af12070 activity and subsequent cyclization with a variety of FQA analogues, including an FQA diastereomer (2'-epi-FQA), which is an intermediate in the fungal biosynthesis of the tremorgenic tryptoquialanine. 2'-epi-FQA is processed by Af12070 to epi-FQD, not epi-FQC, illustrating that the delicate balance in product cyclization regiochemistry can be perturbed by a remote stereochemical center.
DOI: 10.1021/bi201302w