Synthesis and hypoglycemic activity of 5,5-dimethylarylsulfonylimidazolidine-2,4-diones

1-Arylsulfonyl-5,5-dimethylimidazolidine-2,4-diones ( 3a-d ) were prepared by the rearrangement of 3-arylsulfonyl-5,5-dimethylimidazolidine-2,4-diones ( 2a-d ). Compounds ( 2a-d ) were in turn synthesized by the reaction of arylsulfonyl chlorides with 5,5-dimethylimidazolidine-2,4-dione. All the synthesized compounds were characterized by modern spectroscopic techniques. Two of the synthesized compounds, ( 2a ) and ( 3a ), proved to be the stimulators of insulin release when used at concentrations of 100 µ M.


Introduction
3][4] The Narylsulfonylimidazolidine-2,4-diones have, in addition to the sulfonyl moiety, a urea core afforded by the imidazolidine-2,4-dione ring and fulfill all the requirements suggested in the pharmacophoric models for maximum hypoglycemic activity 5 and treatment of hypoglycemic complications. 6Sulfonylimidazolidine-2,4-diones have previously been reported as antidiabetic agents in general and aldose reductase inhibitors in particular. 7,8It has also been reported 9 that imidazolidine-2,4-diones with arylsulfonyl group at position one are more active than their counterparts with substitution at position three.][12] As a continuation of our previous work on the synthesis of arylsulfonylimidazolidine-2,4diones 13,14 and arylsulfonylbenzimidazolone derivatives 15 and their evaluation as hypoglycemic agents, we have synthesized 3-arylsulfonylimidazolidine-2,4-diones (2a-d) and rearranged to 1arylsulfonylimidazolidine-2,4-diones (3a-d) in presence of sodium hydride (Figure 1).The structures of all the synthesized compounds were established by modern spectroscopic techniques and purity ascertained by elemental analysis.The in vitro hypoglycemic activity of two of the compound (2a and 3a) is also being reported.

Results and Discussion
Synthesis 3-Arylsulfonylimidazolidine-2,4-diones (2a-d) were synthesized by the reaction of 5,5dimethylimidazolidine-2,4-dione (1) with aryl sulfonyl chlorides in the presence of triethylamine. 16The 5,5-dimethylimidazolidine-2,4-dione (1) itself was prepared by a standard procedure. 17The synthesis of 3-arylsulfonylimidazolidine-2,4-diones (2a-d) was indicated in the IR spectra by the appearance of the absorptions for anti-symmetric and symmetric O=S=O stretchings in the narrow ranges of 1359-1357 cm -1 and 1168-1148 cm -1 .The synthesis of 2a-d was confirmed in the 1 H-NMR spectra by the presence of only one broad signal for -NH absorptions in the range 8.35 to 8.12 ppm.The non-observance of the signal in the range of 10.00 -9.00 ppm indicated that the more acidic proton has been substituted.The appearance of signals in the aromatic region also confirmed the synthesis.In the mass spectra, the loss of 64 mass units, corresponding to SO 2 , was a common observation.The base peak in all the compounds was observed at m/z 85.For compounds 2b and 2c characteristic isotope peaks were also observed.
The rearrangement of 3-arylsulfonylimidazolidine-2,4-diones (2a-d) in presence of sodium hydride 18 afforded 1-arylsulfonylimidazolidine-2,4-diones (3a-d).The rearrangement to 3a-d was confirmed in the 1 H-NMR spectra by appearance of the -NH signal in the region 10.30 -9.33 ppm.This position of absorption strongly suggests that the more acidic proton is now free and the arylsulfonyl group has migrated to position 1.The mass spectral results were also in accordance with the proposed structures.

Antidiabetic activity
The ability of two of these 5,5-Dimethylarylsulfonylimidazolidine-2,4-diones namely; 5,5dimethyl-1-(4-methylphenyl)imidazolidine-2,4-dione (3a) and 5,5-dimethyl-3-(4methylphenyl)imidazolidine-2,4-dione (2a), to stimulate insulin release was tested using concentrations of 10 µM and 100 µM.The corresponding concentrations of solvent from the stock solutions were 0.2 or 2 %.At a concentration of 2 %, methanol alone increased insulin release; this value was taken as control for the effect of 100 µM of the test agents.The static incubation of insulin-secreting INS-1 cells revealed that at 100 µM, but not at 10 µM, both test agents affected insulin release (Table 1).The 1-substituted compound, however, achieved only a marginally significant increase because of the large scatter of the data, whereas the 3-substituted compound was clearly effective.Tolbutamide, a classical pharmacological stimulator of insulin secretion belonging to the class of sulfonylurea compounds, 19 stimulated insulin release under the same conditions as used to measure the effect of the test agents.At 800 µM, tolbutamide increased the insulin content in the medium to 16.5 ng/ml which has to be compared with 18.1 ± 1.4 ng/ml achieved by 100 µM of 5,5-dimethyl-3-(4-methylphenyl)imidazolidine-2,4-dione (2a).Both the test agents proved to be stimulators of insulin release when used at concentrations of 100 µM.Since both compounds were ineffective at 10 µM, their potency is only moderate, similar to that of tolbutamide, a first generation sulfonylurea.The magnitude of the insulinotropic effect was also similar to that of tolbutamide.From the current data it cannot be decided whether there is difference between the insulinotropic efficiencies of these two isomeric compounds.At any rate, it seems worthwhile to check whether these compounds have essentially the same mechanism of action as the sulfonylureas, i.e. closure of ATP-dependent potassium channels, leading to Ca 2+ influx into the cell and stimulation of secretion, or whether they affect a new therapeutic target.
Incited by these results, the in vivo hypoglycemic activities of these and related compounds are underway in this laboratory.Some excellent in vivo hypoglycemic results have been obtained and will be published separately. 20perimental Section General Procedures.Melting points of the compounds were determined in open capillaries using Gallenkemp melting point apparatus and are uncorrected.IR spectra were recorded on a FTS 3000 MX, Bio-Rad Merlin (Excalibur Model) spectrophotometer either as KBr discs while 1 H-and 13 C-NMR spectra were recorded on a Bruker Avance 300 MHz NMR spectrophotometer as acetone-d 6 solutions using TMS as an internal standard.EIMS were measured on a MAT-112-S machine at 70 eV and Elemental analysis was performed on Leco CHNS-932 (USA) Leco Corporation.
General method for the synthesis of 3-arylsulfonylimidazolidine-2,4-diones 16 To a well stirred mixture of imidazolidine-2,4-dione (4.8 mmol), triethylamine (4.8 mmol) and catalytic amounts of DMAP, was dropwise added a solution of arylsulfonyl chloride (5.8 mmol) in an appropriate volume of dichloromethane and the reaction mixture was stirred at room temperature for three hours.The reaction mixture was diluted with 1N HCl till pH 2 and extracted with dichloromethane (3 × 25 mL).The crude product after evaporation of the solvent was recrystallized from ethyl acetate to afford a crystalline powder.General method for the synthesis of 1-arylsulfonylimidazolidine-2,4-diones 18 To a solution of 3-arylsulfonylimidazolidine-2,4-dione (0.001 mol) in dry benzene (15 ml), sodium hydride (0.0012 mol) was added and the mixture refluxed under argon atmosphere for two hours.The solvent was evaporated and petroleum ether was added.The sodium salt of 1arylsulfonylimidazolidine-2,4-dione so precipitated was filtered, dissolved in water, neutralized with IN HCl and extracted with ethyl acetate (3 × 25 mL).After evaporation of the solvent, the rearranged product was recrystallized from ethyl acetate to afford a white crystalline powder.Measurement of insulin secretion 5,5-Dimethyl-1-(4-methylphenyl)imidazolidine-2,4-dione (3a) and 5,5-Dimethyl-3-(4methylphenyl)imidazolidine-2,4-dione (2a) were prepared as a 5 mM stock solution in methanol.Measurement of insulin secretion was performed by static incubation of ca.0.5 × 10 6 insulinsecreting INS-1 cells in 12-well dishes.The incubation medium was a Krebs-Ringer buffer containing 5 mM glucose.After incubation for 1 h at 37 °C, 500 µl of the incubation medium were aspirated from each well and centrifuged to pellet aspirated cells.Insulin content in the supernatant was determined by a sandwich ELISA according to the instructions of the manufacturer (Mercodia AB, Uppsala, Sweden).