1. Potential carcinostatics. 4. Synthesis and biological properties of erythro- and threo-beta-fluoroaspartic acid and erythro-beta-fluoroasparagine
M J Wanner, J J Hageman, G J Koomen, U K Pandit J Med Chem. 1980 Jan;23(1):85-7. doi: 10.1021/jm00175a017.
(E)- and (Z)-Di-tert-butyl 2-amino-3-fluoro-2-butene-1,4-dioate [(E)- and (Z)-2] were synthesized in two ways: (a) by elimination of hydrogen fluoride from di-tert-butyl beta,beta-difluoroaspartate under the influence of 1,5-diazabicyclo[4.3.0]non-5-ene and (b) by amination with the ammonium acetate of di-tert-butyl monofluorooxaloacetate (3), obtained via condensation of tert-butyl monofluoroacetate with di-tert-butyl oxalate. Reduction of 2 with sodium cyanoborohydride yielded a mixture of di-tert-butyl monofluoroaspartates in which the erythro isomer constituted the major product. The structure of this isomer (4a) was established by X-ray crystallographic analysis of the corresponding acid 5a. Esterification of 5a to the beta-methyl ester 6, followed by aminolysis, yielded erythro-beta-fluoroasparagine (7). Tests with 5a and 7 in the L-5178Y test system showed that the compounds exhibited toxicity at levels at which no antitumor activity was observed.
2. Potential inhibitors of L-asparagine biosynthesis. 4. Substituted sulfonamide and sulfonylhydrazide analogues of L-asparagine
S Brynes, G J Burckart, M Mokotoff J Med Chem. 1978 Jan;21(1):45-9. doi: 10.1021/jm00199a008.
Several N-substituted sulfonamides and N'-substituted sulfonylhydrazides have been prepared as sulfur analogues of L-asparagine with the potential of acting as inhibitors of L-asparagine synthetase (ASase, from Novikoff hepatoma). L-Cysteine was converted in known steps to N-carboxy-3-(sulfonylchloro)-L-alanine dibenzyl ester (1). Condensation of 1 with O-benzylhydroxylamine, p-(fluorosulfonyl)benzylamine, or monoethyl fumarylhydrazide (9), followed by deblocking with HF, gave 3-(hydroxysulfamoyl)-L-alanine (3a), 3-[p-(fluorosulfonylbenzyl)]sulfamoyl-L-alanine (3c), and 3-sulfo-L-alanine S-[2-[(E)-3-(ethoxycarbonyl)acryloyl]hydrazide] (3e), respectively. Similarly, 1 with 2-chloroethylamine and deblocking with H2-Pd gave 3-[(2-chloroethyl)sulfamoyl]-L-alanine (3b). tert-Butyl carbazate was allowed to react with 1 and the tert-butyl group was removed with HCl. The resulting sulfonylhydrazide 7 was condensed with p-(fluorosulfonyl)benzoyl chloride and then deblocked with HF to give 3-sulfo-L-alanine S-[2-[P-(fluorosulfonyl)benzoyl]hydrazide] (3d). The inhibition of ASase by 3a-e at 2 mM was 97, 0, 30, 43, and 37%, respectively, and 3a was competitive with L-aspartic acid. Neither 3a nor 3e was effective in increasing the life span of mice bearing P-388 lymphocytic leukemia.
3. DL-threo-beta-Fluoroaspartate and DL-threo-beta-fluoroasparagine: selective cytotoxic agents for mammalian cells in culture
A M Stern, B M Foxman, A H Tashjian Jr, R H Abeles J Med Chem. 1982 May;25(5):544-50. doi: 10.1021/jm00347a013.
Absolute configuration assignments have been made for the diastereomers of DL-beta-fluoroaspartate by X-ray analysis. The cytotoxicity of these isomers against various mammalian cells was examined. DL-threo-beta-Fluoroaspartate shows selective cytotoxicity. Growth of the most sensitive cells is completely inhibited by 13 micrometers DL-threo-beta-fluoroaspartate in the presence of 100 micrometers L-aspartate, a component of the culture medium. A difference in the rate of transport of DL-beta-fluoroaspartate among the cells studied is an important factor determining cell specificity. For those cells that are sensitive to DL-beta-fluoroaspartate, the threo isomer is, in all cases, more potent than the erythro isomer. Radioactivity derived from L-threo-beta-fluoro[14C]aspartate is incorporated into proteins at a rate comparable to the rate of incorporation from L-[14C]aspartate. We synthesized DL-threo-beta-fluoroasparagine. This compound is also cytotoxic but less specific and less potent than DL-threo-beta-fluoroaspartate. However, the cell specificity can be enhanced in the presence of 1 mM L-aspartate, which can protect some cells but not others from the cytotoxic effects of DL-threo-beta-fluoroasparagine. Jensen sarcoma cells, which require asparagine, are not protected by L-aspartate. Therefore, a combination of L-aspartate and DL-threo-beta-fluroasparagine can be used to inhibit specifically the growth of asparagine-requiring tumors.
