2,4-Pentanedione, reaction with amino

In the experiments first described, 2-amino-2-deoxy-D-glucose was heated with an excess of the /3-dicarbonyl compound in the absence of solvent. The product so obtained from ethyl acetoacetate, m.p. 142°, [a]n 49.7°, had an analysis corresponding to that for ethyl 2-methyl-5-(D-ara6mo-tetrahydroxybutyl)pyrrole-3-carboxylate and was considered to have this structure (1). In the reaction with 2,4-pentanedione, a material (m.p. 98°, Md — 25.1°) was obtained which was described as 3-acetyl-2-methyl-5-(D-ara5fno-tetrahydroxybutyl)pyrrole (2). Boyer and Furth" repeated the latter reaction, but in methanol solution, and obtained a product, m.p. 133°, whose analytical data were in agreement with those for structure (2). 

Base-catalyzed reactions of amino sugars with 2,4-pentanedione in a nonaqueous solvent (piperidine-triethylamine-methanol) have also been reported. The products obtained under these conditions from 2-amino-2-deoxy-D-glucose are 3-acetyl-2-methyl-5-(D-ami)OTo-tetrahydroxybutyl)-pyrrole (2) (in about 90% yield) and 2-deoxy-2-n(4-oxopent-2-enyl)-amino]-D-glucose (28). Proofs that structure (28) is correct were (a) the ultraviolet absorption, typical of a -amino a,j3-unsaturated ketone, (b) a positive test with the ferric chloride reagent, and (c) quantitative... 

Cornforth and coworkers and Gottschalk have expressed the view that the reaction of 2-amino-2-deoxy-n-glucose with pyruvic acid (and with 2,4-pentanedione) begins with the formation of a Schiff base [such as (85)], followed by an intramolecular aldol reaction to compounds (86). This interpretation cannot be extended to the reactions of nonnitrogenous sugars, and can only be applied in a modified way to the iV-alkylamino and M-arylamino sugars. Such compounds as (87) or (88) could be the... 

Reaction of 6-halopurines with Michael acceptors under Heck conditions gives N- -substituted hypoxanthine derivatives <00CCC797>. Reactions of a series of 1-aminobenzimidazoles and l-amino-3-methylbenzimidazolium chlorides with 2,4-pentanediones afford pyridazino[l,6-a]benzimidazoles and 2-pyrazolylanilines, the product ratio depending on conditions and on the electronic character of the substituents at the benzene moiety <00BMC37>. Cyclization reactions of adenine derivative 75 with different amines or hydrazine afford tricyclic polyaza compounds 76 <00CCC1109>. 

Another class of pyrrole derivative may be obtained by the interaction of l-amino-l-deoxy-2-ketoses or 2-amino-2-deoxyaldoses with a jQ-dicarbonyl compound. Unlike the previous type (which is N-substituted), these pyrrole derivatives have a tetrahydroxybutyl group in the a- or /8-position with respect to the nitrogen atom of the ring, in addition to other groups arising from the dicarbonyl compound used in the condensation. The formation and reactions of this type of pyrrole derivative have been discussed in detail in two articles in this series48,49 they will, therefore, only be treated briefly. 1-Amino-l-deoxy-D-fructose (53) reacts with 2,4-pentanedione to give50 pyrrole derivative 54a similar pyrroles were obtained with ethyl acetoace-tate,50,51 which yields 54b. 

The most specific and frequently used assay to quantify 2-deoxy-2-amino sugars employs the condensation of the carbohydrate with 2,4-pentanedione in basic solution. The product (a pyrrole derivative) is then reacted with p-dimethylaminobenzaldehyde to form a chromogen that has a maximum absorbance at 530 nm (Fig. 11-2). Although both 6-deoxy-6-amino and 3-deoxy-3-amino sugars can also be analyzed using the Elson-Morgan reaction, the chromogens... 

Terada and co-workers reported the direct Mannich reaction of 1,3-pentanedione with N-Boc-aldimines catalyzed by 21c, leading to (3-amino ketones with excellent enantioselectivities (Equation 10.36) [75]. 

This product is probably formed by condensation (involving the Strecker degradation of an amino acid) of pyruvaldehyde with 2,3-pentanedione (Wang et al., 1969). It is formed in the Maillard reaction of the dipeptide Ala-Asp (alanine-aspartic acid) with glucose. 

The reaction of l-amino-l-deoxy-n-fructose with 2,4-pentanedione gives 3-acetyl-2-methyl-4-(D-araZ)mo-tetrahydroxybutyl)pyrrole (20). Acetylation of this compound yields a tetra-O-acetyl derivative, and periodate oxidation of (20) furnishes 4-acetyl-5-methylpyrrole-3-carboxaldehyde (24), which can be subsequently oxidized to 4-acetyl-5-methylpyrrole-3-carboxylic acid (26). 

In the reactions of 2-amino-2-deoxy-D-glucose with some /3-dicarbonyl compounds (such as ethyl acetoacetate, 2,4-pentanedione, or pyruvic acid) in alkaline solution, pyrroles lacking the tetrahydroxybutyl chain are obtained. The loss of this group cannot occur with the already formed (tetrahydroxybutyl)pyrroles, because these compounds, as exemplified by 3-acetyl-2-methyl-5-(D-ora wo-tetrahydroxybutyl)pyrrole (2), remain unchanged at the pH (9-10) of the reaction. The fission of the sugar chain most probably occurs for one of the intermediates of the reaction, for instance (79), and it may be formulated as a concerted-elimination reaction catalyzed by the hydroxyl ion, as indicated in Scheme C. The... 

On the basis of an intermediate (89), similar to (86), for the reaction of 2-amino-2-deoxy-D-glucose with 2,4-pentanedione, the formation of 2-methylpyrrole has been explained by assuming a concerted elimination initiated by the attack of the hydroxyl ion on the acetyl group, so as to give compound (90), followed by a fission (envisaged as a retroaldol type of reaction) of the tetrahydroxybutyl chain, as shown. 

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