Diazoacetyl derivatives

Another good example of the use of affinity labels involves pepsin, and is illustrated in Chapter 16, equations 16.28 and 16.29. The enzyme has two catalyt-ically important aspartic acid residues, one ionized and the other un-ionized. The ionized carboxylate is trapped with an epoxide, which, of course, requires the reaction of a nucleophilic group. The un-ionized carboxyl is trapped with a diazoacetyl derivative of an amino acid ester ... 

The diazomethyl ketone functional group was first observed to be an affinity label by Buchanan and co-workers who showed that the antibiotic azaserine, an O-diazoacetyl derivative, 9 inhibited an enzyme in the biosynthesis of purine by alkylation of a cysteine residue. 10 The acid protease pepsin was then observed to be inhibited by peptidyl diazomethyl ketones in the presence of copper ions with the resulting esterification of an aspartate residue. 11 Two peptidyl diazomethyl ketones, Z-Phe-CHN2 and Z-Phe-Phe-CHN2, were found to irreversibly inactivate papain, a cysteine protease. 12 Since these reports, many peptidyl diazomethyl ketones have been prepared primarily as inhibitors of various cysteine proteases. 7 Peptidyl diazomethyl ketones are also synthetic intermediates and have been used to prepare chloromethyl ketones (Section 15.1.3), 13 bromomethyl ketones (Section 15.1.3), acyloxymethyl ketones, 14 and (i-peptides. 15 A few peptidyl diazoalkyl ketones have been reported. 16,17 ... 

Clearly, the choice is restricted by the absorption spectrum of the label. However, diazoketone and diazoacetyl derivatives, for example, possess two absorption bands - one at 254 nm (s 7000) and one at 350 nm e 10). Since carbenes may be produced by irradiation at either wavelength the question which immediately arises is which absorption should be used. The potential gain from irradiating with the shorter wavelength is that the intermediate formed is more reactive than that generated at the longer wavelength. This would enhance the likelihood... 

The imidazo[5,l -e]-l.2,3,5-Letrazine-8-carbonyl chloride 17 reacts preferentially with nucleophiles (Nu ) at the 8-carbonyl group rather then at the 4-oxo group, allowing the preparation of a wide range of ester, thioester, amide, hydroxamic acid, hydrazide, sulfoximide, azide, and diazoacetyl derivatives.42... 

Does the preparation react with the ligand analog in the dark during the time required for a typical photolysis During prolonged pho-tolyses, e.g., diazo compounds at 350 nm, a diazoacetyl derivative may label the receptor in a dark reaction by an electrophilic mechanism. Analysis of such incubation mixtures also tests for removal of noncova-lently bound material in the work-up procedure. 

Whereas pyrrole was reported not to give N/H insertion by ketocarbenoids, such a reaction mode does occur with imidazole Copper-catalyzed decomposition of ethyl diazoacetate at 80 °C in the presence of imidazole gives ethyl imidazol- 1-ylacetate exclusively (93 %) small amounts of a C-alkylated imidazole were obtained additionally under purely thermal conditions 244). N/H insertion also takes place at benzimidazole 245 a). The reaction is thought to begin with formation of an N3-ylide, followed by N1 - C proton transfer leading to the formal N/H insertion product. Diazomalonic raters behave analogously however, they suffer complete or partial dealkoxycarbonylation under the reaction conditions 244) (Scheme 34). N-alkylation of imidazole and benzimidazole by the carbenoids derived from co-diazoacetophenone and 2-(diazoacetyl)naphthalene has also been reported 245 b>. 

Suga et al. (197) reported the first stereocontrolled 1,3-dipolar cycloaddition reactions of carbonyl ylides with electron-deficient alkenes using a Lewis acid catalyst. Carbonyl ylides are highly reactive 1,3-dipoles and cannot be isolated. They are mainly generated through transition metal carbenoid intermediates derived in situ from diazo precursors by treatment with a transition metal catalyst. When methyl o-(diazoacetyl)benzoate is treated with A-methylmaleimide at reflux... 

Derivatives of fentanyl and sufentanil with chemo- and photoaffinity functionalities attached to the anilido nitrogen (e.g., NCOCH2Br, NCOCH=N2) have been reported, but affinity labeling experiments performed with theses compounds on brain tissue met with little success. Some of the compounds, notably the diazoacetyl analog of cis 3-methylfentanyl, displayed high binding affinities.(60)... 

Diazoacetylation, Diazoacetyl chloride (1) reacts with alcohols, phenols, thiols, and amines in the presence of triethylamine to afford the diazoacetic ester or amide derivatives 2 in high yield. ... 

Giraldi T., Nisi C. and Sava G. (1977). Antimetastatic effects of N-diazoacetyl-glycine derivatives in C57BL mice. J. Natl. Cancer Inst. 58, 1129-1130. Giraldi, T., Perissin, L., Zorzet, S., Piccini, P. and Rapozzi, V. (1989). Effects of stress on tumor growth and metastasis in mice bearing Lewis lung carcinoma. Eur. J. Cancer Clin. Oncol. 25, 1583-1588. 

Indeed in the synthesis of diazoketones described in the synthesis of haloketones, this very process takes place. Diazoacetyl and diazoketone derivatives can also decompose via carbenes instead of carbonium ions even in the absence of irradiation. For example... 

The syntheses of diazoacetyl compounds have been described ( 5.8.2). Because pf their potential utility, the synthesis of an ethyl diazomalonyl derivative and an aryl azide precursor of carbenes and nitrenes, respectively, are presented below. 

Carbenes, generated by photolysis of di- and tetrachloro-o-quinone diazides, react with oxetane in a 1 3 ratio to afford 15-membered crown ethers. Benzocrown ether 675 was obtained in 16% yield (91CB1865). Derivatives of macrocyclic crown ethers with four or five oxygen atoms in a ring were synthesized by Cu(acac)2-catalyzed cyclization of a,polyethylene glycols. 20-26-Membered crown-4(5) ethers 676 were prepared from the above-mentioned diazo ketones with tri- or tetra-ethylene glycols in 7-26% yields. Treatment of l,8-bis(diazoacetyl)octane with dodecane-l,12-diol under the same conditions results in a mixture of 52-membered tetraether 646 (40%) and compound 645 (81CC616). 

According to a recent report, however, the carbonyl ylides formed under these conditions may isomerize and lead to adducts different from those normally expected87. Thus, (5)-l-acetyl-2-(diazoacetyl)pyrrolidine (8). derived from /V-acetyl-i.-proline, upon treatment with dimethyl butynedioate in the presence of a catalytic amount of rhodium(II) acetate dimer at 25 °C affords only 10% of the expected adduct dimethyl 5,8-epoxy-2,3,5,8,9,9a-hexahydro-5-methyl-9-oxo-lH-pyrrolo[l, 2-o]azepine-6,7-dicarboxylate (9). Instead, dimethyl 1,2,8,9-tetrahydro-5-methyl-l-oxo-3a//,7//-furo[3,2-g]pyrrolizine-3a,4-dicarboxylate (10) is obtained in 87% yield. The formation of this product is explained via an isomeric ylide87 and thus occurs with complete loss of chiral information. 

Details have appeared of the preparation of the molecules (760a—d) by BF3-catalysed cyclization of diazoacetyl-tetrahydro-2-naphthol or -hexahydrophen-anthrene derivatives. ... 

Intramolecular C-H insertion reaction of the a-diazoacetyl ester derived from compound (1) is also reported recently. The cyclization, found to proceed with excellent regio- and stereoselectivities, and has been used as key step to synthesize natural products. 

O-Diazoacetyl-ij-serine (Azaserine). The derivative may be prepared by selective diazotization of 0-glycyl-L-serine as reported by Nicolaides et aZ. It may be recrystallized from water-ethanol m.p. 153°-155° (dec.) ymax = 249.5 nm = 20,000. French et aZ. prepared 0-diazo-[2- C] acetyl L-serine by a modification of the above-cited procedure. 

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