WO1996016649A1 - 2-heterocyclyloxy and thiomethyl-1,2,5-thiadiazolidin-3-one 1,1-dioxides and compositions and method of use thereof - Google Patents

Abstract

2-Heterocyclyloxy and thiomethyl-1,2,5-thiadiazolidin-3-one 1,1-dioxides, pharmaceutical compositions containing them and methods for the treatment of degenerative diseases utilizing them.

Description

2-Heterocyclyloxy and Thiomethyl-1, 2, 5-Thiadiazolidin-3-

One 1,1-Dioxides and Compositions and

Method of use Thereof

Background of The Invention

(a) Field of The Invention

The invention relates to 2-heterocyclyloxy and thiomethyl 1 , 2 , 5-thiadiazolidin-3-one 1 , 1-dioxides , to pharmaceutical compositions containing the same and to the method of use thereof in the treatment of degenerative diseases.

(b) Information Disclosure Statement

The inhibition of proteolytic enzymes by nontoxic reagents is useful in the treatment of degenerative disorders, such as emphysema, rheumatoid arthritis and pancreatitis, in which proteolysis is a substantive element.

Protease inhibitors are widely utilized in biomedical research. Serine proteases are the most widely distributed class of proteolytic enzymes. Some serine proteases are characterized as chymotrypsin-like or elastase-like based upon their substrate specificity.

Chymotrypsin and chymotrypsin-like enzymes normally cleave peptide bonds in proteins at a site at which the amino acid residue on the carboxy1 side is typically Trp, Tyr, Phe, Met, Leu or another amino acid residue which contains aromatic or large alkyl side chains.

Elastase and elastase-like enzymes normally cleave peptide bonds at a site at which the amino acid residue on the carboxyl side of the bond is typically Ala, Val, Ser, Leu or other similar, smaller amino acids.

Both chymotrypsin-like and elastase-like enzymes are found in leukocytes, mast cells and pancreatic juice in higher organisms, and are secreted by many types of bacteria, yeast and parasites.

Cha, Biochem. Pharmacol., 1975. 24, 2177-2185, discusses kinetic approaches to the study of the binding of inhibitors to

-1- macromolecules, such as enzymes, and methods for the determination of such parameters as the inhibition constants, reaction rates and bound and unbound enzyme concentrations.

Groutas et al . , Biochemical and Biophysical Research Communications 1994 , 198(1), 341-349 disclose compounds of the formula:

wherein Ri is H, methyl, benzyl, CH2C00t-Bu or CH2COOBzl and their in vitro inhibitory activity towards human leukocyte elastase.

Muller and DuBois, J. Org. Chem. 1989. 54, 4471-4473 disclose compounds of the formula:

wherein R is H, CH3 , benzyl or (CH2)2SCH3. The compounds were tested for sweet taste activity and were found to be not sweet or to have sweetness potencies of less than 10 times sucrose.

Lee et al., J. Org. Chem. 1989. 54, 3077-3083 disclose the synthesis of compounds of the formula:

wherein R is phenethyl, phenyl or 1-naphthyl. No utility is disclosed for these compounds.

Lee and Kohn, Journal of Pharmaceutical Sciences 1990. 79(8), 716-718 disclose compounds of the formula:

-2-

wherein R^ is phenethyl, phenyl or 1-naphthyl and R^ ' is hydrogen, or R^ and R^ ' are both phenyl. The compounds were tested for anticonvulsant activity and three of the four compounds were found to be devoid of anticonvulsant activity.

Hanewacker et al. , Arch. Pharm. 1993. 326, 497-498 disclose the synthesis of compounds of the formula:

wherein R is CH2CH(CH3)2, cyclopropylmethyl, CH2Ph, (CH2)2Ph, 2- furanylmethyl, 1-naphthylmethyl, or 3-indolylethyl.

Unterhalt and Hanewacker, Arch. Pharm. 1988. 321, 375-376 disclose the synthesis of compounds of the formula:

wherein R is hydrogen, methyl, isopropyl, CH2CH(CH3)2 or benzyl without an indication of utility.

Unterhalt and Hanewacker, Arch. Pharm. 1988. 321, 749-751 disclose the synthesis of compounds of the formula:

^•3-

wherein R=CH3 , R!=H and R²=3-indolylmethyl; R=CH3 , R¹=H, and R²=phenyl; R=C2H5, R¹=H, and R²=phenyl; R=isopropyl, R¹=H, and R²=phenyl; R=methyl, R¹=CH3θ(0)CCH2, and R²=H; R=CH3, R¹=H0(0)CCH2 and R²=H; R=CH3, R¹=C2H5 and R²=phenyl; R=R¹=R²=CH3 ; and R=C2H5,

Aouf et al., Tetrahedron Letters 1991. 32(45), 6545-6546 disclose the synthesis of 4-phenylmethyl-l,2, 5-thiadiazolidin-3- one 1,1-dioxide.

Dewynter et al. , Tetrahedron 1993 , 49(1), 65-76 disclose the synthesis of compounds of the formula:

wherein R is CH2P or CH2CH(CH3) (C2H5) .

Dunlap et al. , U.S. Patent 5,236,917, issued August 17, 1993 disclose a series of 2-substituted saccharin derivatives, such as 4- (1-methylethyl) -2-[ (3-oxo-l,2, 5-thiadiazolidin-2-yl) ethyl] -1,2- benzisothiazol-3 (2H) -one S, S, 1 , 1-tetraoxide, 2- (1-methyl-lH- tetrazol-5-yl-thiomethyl) saccharin and various 2-halomethy1 saccharin derivatives, which are stated to be useful in the treatment of degenerative diseases.

Strasser et al. , German Patent Application DE 4141218, published June 17, 1993, disclose a series of thiadiazolidin-3-one 1,1-dioxide derivatives as intermediates in the synthesis of various 1, 1-dioxo- [1, 2, 6] thiadiazinecarboxamides which are stated to be potentially useful as analgesics, antipyretics and inflammation inhibitors. Summary of the Invention The invention relates to compounds of the Formula I:

I wherein R^ is hydrogen, lower-alkyl, or phenyl-lower-alkyl; R² is hydrogen, lower-alkyl, or phenyl-lower-alkyl; R is hydrogen, or lower-alkyl; or R² and R^ together are -(CH2)n~ wherein n is 3 or 4;

X is 0 or S; and R⁴ is a heterocycle selected from the group consisting of tetrazolyl, pyrazolyl, imidazolyl, thiadiazolyl, thiazolyl, and triazolyl which is attached through any available carbon atom thereof to the -X- group (or said heterocycle substituted on any available carbon atom thereof by lower-alkyl, or trihalomethyl; and/or on any available nitrogen atom thereof by lower-alkyl, or phenyl); or a pharmaceutically acceptable acid- addition salt thereof; or where applicable, an enantiomer or a racemic mixture thereof .

The compounds of the present invention inhibit the activity of serine proteases, specifically human leukocyte elastase, and are thus useful in the treatment of degenerative disease conditions such as emphysema, rheumatoid arthritis, pancreatitis, cystic fibrosis, chronic bronchitis, adult respiratory distress syndrome, inflammatory bowel disease, psoriasis, bullous pemphigoid, periodontal disease, and alpha-1-antitrypsin deficiency.

Preferred compounds of the Formula I above are those wherein R¹ is hydrogen, or lower-alkyl; R² is hydrogen, or lower-alkyl; R-⁵ is hydrogen, or lower-alkyl; or R² and R^ together are -(CH2)n~ wherein n is 3 or 4; X is 0 or S; and R⁴ is a heterocycle selected from the group consisting of tetrazolyl and pyrazolyl (or said heterocycle substituted on any available carbon atom thereof by trihalomethyl; and/or on any available nitrogen atom thereof by phenyl); or a pharmaceutically acceptable acid-addition salt thereof; or where applicable, an enantiomer or a race ic mixture thereof .

Particularly preferred compounds of the Formula I above are those wherein R¹' R², R3 and X are as defined directly above; and R⁴ is a heterocycle selected from the group consisting of 5- tetrazolyl and 5-pyrazolyl (or said heterocycle substituted on any available carbon atom thereof by trifluoromethyl; and/or on any available nitrogen atom thereof by phenyl) ; or a pharmaceutically acceptable acid-addition salt thereof; or where applicable, an enantiomer or a racemic mixture thereof.

Preferred species of the Formula I above are 2- (1-phenyl-lH- tetrazol-5-yl-thiomethyl) -4-propyl-5-methyl-l,2, 5-thiadiazolidin- 3-one 1,1-diόxide and 2- (l-phenylpyrazol-5-yl-oxymethyl) -4- (3- methylbutyl) -5-methyl-l,2,5-thiadiazolidin-3-one 1, 1-dioxide.

The invention further relates to a pharmaceutical composition for the treatment of degenerative diseases which comprises a pharmaceutically acceptable carrier, adjuvant, diluent or vehicle together with an effective proteolytic enzyme inhibiting amount of a compound of the Formula I.

The invention further relates to a method for the treatment of degenerative diseases which comprises administering to a patient in need of such treatment an effective proteolytic enzyme inhibiting amount of a compound of the Formula I.

Detailed Description Inclusive of Preferred Embodiments

The term lower-alkyl as used herein means linear or branched hydrocarbon chains having one to about five carbon atoms and thus includes methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, 3- methylbutyl; n-pentyl, and the like.

The term halogen, halo, or halide as used herein means chlorine, bromine, iodine, and fluorine.

The numbering system used throughout this specification is shown in the ring system which is illustrated below. This ring

system is named in the chemical literature as a 1 , 2 , 5 - thiadiazolidin-3 -one 1 , 1-dioxide .

The synthesis of the compounds of the invention may be outlined as shown in Scheme A :

SCHEME A

II

A suitably substituted 2-halomethyl-l, 2, 5-thiadiazolidin-3-one 1,1-dioxide derivative of the formula II, wherein X' is a halogen, preferably chlorine, in a suitable organic solvent, such as dimethylformamide, is treated with an excess of a compound of the formula III, wherein M⁺ is an alkali metal, such as sodium or cesium, at a temperature in the range of about room temperature up to the boiling point of the solvent used, to afford the compounds of the formula I.

It will be appreciated that the compounds of the formula I possess an asymmetric carbon at position C-4 of the 1,2,5- thiadiazolidin-3-one 1,1-dioxide ring and are thus capable of existing as enantiomers . Unless otherwise specified herein, the invention is intended to extend to each of the enantiomeric forms including the racemates. In some cases there may be advantages, i.e. greater potency, to using a particular enantiomer when compared to the other enantiomer or the racemate in the treatment

-7- of degenerative diseases and such advantages can be readily determined by those skilled in the art. The separate enantiomers may be synthesized from chiral starting materials or the racemates may be resolved by conventional procedures which are well known in the art of chemistry such as chiral chromatography, fractional crystallization of diastereomeric salts and the like.

The compounds of Formula I are useful both in the free base form and in the form of acid-addition salts, and, both forms are within the purview of the invention. The acid-addition salts are often a more convenient form for use; and in practice, use of the salt form inherently amounts to use of the base form. The acids which can be used to prepare the acid-addition salts include preferably those which produce, when combined with the free base, pharmaceutically-acceptable salts, that is, salts whose anions are relatively innocuous to the animal organism in pharmaceutical doses of the salts, so that the beneficial properties inherent in the free base are not vitiated by side effects ascribable to the anions. In practicing the present invention it is convenient to use the free base form or the hydrochloride, fumarate, toluenesulfonate, methanesulfonate or maleate salts. However, other appropriate pharmaceutically acceptable salts within the scope of the invention are those derived from other mineral acids and organic acids. The acid-addition salts of the basic compounds are prepared by standard procedures well known in the art which include, but are not limited thereto, dissolving the free base in an aqueous alcohol solution containing the appropriate acid and isolating the salt by evaporating the solution, or by reacting the free base and an acid in an organic solvent, in which case the salt separates directly, or is precipitated with a second organic solvent, or can be obtained by concentration of the solution.

Although medicinally acceptable salts of the basic compounds are preferred, all acid-addition salts are within the scope of the present invention. All acid-addition salts are useful as sources of the free base form even if the particular salt per se is desired only as an intermediate product, as, for example, when the salt is formed for purposes of purification or identification, or when it is used as an intermediate in preparing a medicinally acceptable salt by, for example, ion exchange procedures.

The suitably substituted 2-halomethyl-l,2, 5-thiadiazolidin-3- one 1,1-dioxides of the formula II, which are required for the synthesis of the compounds of the formula I, can be prepared as shown in Scheme B:

SCHEME B

IV VI

'

II

A suitably substituted 1,2, 5-thiadiazolidin-3-one 1,1-dioxide of the formula IV, or an ammonium salt thereof, or a cesium salt thereof (prepared by the treatment of a compound of the formula IV in a lower-alkanol solvent, i.e. methanol, with cesium carbonate at a temperature of about room temperature) , in a suitable organic solvent, such as toluene, dimethylformamide or a mixture of said solvents, is treated with an excess of a halomethyl phenyl sulfide, wherein X' is a halogen, preferably chlorine, in the presence of a catalytic amount of a tetralower-alkylammonium halide, such as tetrabutylammonium bromide, (note, however, that the use of the tetralower-alkylammonium halide is optional when the cesium salt of the compound of the formula IV is utilized) , at a temperature in the range of about room temperature up to the boiling point of the solvent or solvent mixture used, preferably at the boiling point of the solvent or solvent mixture used, to afford the compounds of the formula VI. The compound of the formula VI can then be treated with an excess of a sulfuryl halide of the formula SO2X ' 2. wherein X' is a halogen, preferably chlorine, in a suitable organic solvent, such as methylene chloride, at a temperature of about room temperature, to afford the compounds of the formula II.

The suitably substituted 1, 2 , 5-thiadiazolidin-3-one 1,1- dioxides of the formula IV can be prepared as shown in Scheme C:

SCHEME C

VII IV

A suitably substituted compound of the formula VII wherein R is lower-alkyl, in an appropriate lower-alkanol solvent, such as methanol, is treated with an excess of an alkali metal lower- alkoxide; i.e. sodium methoxide, at a temperature in the range of about room temperature up to the boiling point of the solvent used, followed by treatment with a proton source, such as BIO-RAD® 50W-X8 H⁺ ion exchange resin, to afford the compounds of the formula IV.

Alternatively, when the compounds of the formula IV wherein R3 is lower-alkyl are desired, one can proceed as illustrated in Scheme D:

^■10-

SUBSTΓΓUTE SHEET (RULE 26) SCHEME D

XI IV

A compound of the formula IV wherein R^ is hydrogen, is treated with an excess of a benzyl halide of the formula VIII, wherein X' is a halogen, preferably bromine, in a suitable organic solvent, i.e. toluene, dimethylformamide, or a mixture thereof, in the presence of a catalytic amount of a tetralower-alkylammonium halide, preferably tetrabutylammonium bromide, at a temperature in the range of about room temperature up to the boiling point of the solvent, or solvent mixture used, to afford the compounds of the formula IX. The compounds of the formula IX can then be treated with the excess of an alkylating agent (R^x*) of the formula X, wherein R3 is lower-alkyl and X' is a halogen, preferably iodine, in a suitable organic solvent, such as tetrahydrofuran, in the presence of an excess of a base, such as potassium tert-butoxide, at a temperature in the range of about 0^*C up to the boiling point of the solvent used, preferably at a temperature in the range of about O'C up to about room temperature, to afford a compound of the formula XI. The compound of the formula XI can then be debenzylated by treatment with an excess of an appropriate hydrogen donor, preferably ammonium formate, in the presence of an appropriate catalyst, preferably palladium on carbon, in a

-11-

SUBSTΓΓUTE SHEET (RULE 26) suitable lower-alkanol solvent, such as methanol, at a temperature in the range of about room temperature up to the boiling point of the solvent used, preferably at a temperature of about room temperature, to afford the compounds of the formula IV wherein R3 is lower-alkyl.

The compounds of the formula VII, which are required for the synthesis of the compounds of the formula IV, can be prepared as illustrated in Scheme E:

SCHEME E

VII

A halosulfonyl isocyanate of the formula XII, wherein X is a halogen, preferably chlorine, is treated with an excess of an α- amino acid ester of the formula XIII, wherein R is lower-alkyl and X^" is a halogen, preferably chlorine, and an excess of benzyl alcohol, in the presence of an excess of a base, such as triethylamine, in an appropriate organic solvent, such as methylene chloride, at a temperature in the range of about -10"C up to about room temperature, to afford a compound of the formula XIV (Note, if desired, the α-amino acid ester can be used as the limiting reagent rather than the halosulfonyl isocyanate) . The compound of the formula XIV can then be hydrogenated at a hydrogen

-12- pressure of about 50-55 psi, in a lower-alkanol solvent, such as methanol, in the presence of a catalyst, preferably palladium on carbon, to produce the compounds of the formula VII.

The compounds of the formula III are either commercially available, or they can be prepared by procedures known in the art

(see, for example, U.S. Patent 5,236,197 which is incorporated herein by reference) , or by the procedures described hereinbelow in the examples. The halomethyl phenyl sulfides of the formula V, the benzyl halides of the formula VIII, the alkylating agents

(R3X¹) of the formula X, halosulfonyl isocyanates of the formula XII and the α-amino acid esters of the formula XIII are either commercially available, or they can be prepared by procedures known in the art, or by the procedures described hereinbelow in the examples.

The structures of the compounds of the invention were established by the mode of synthesis, and by one or more of elemental analysis, and infrared, nuclear magnetic resonance and mass spectroscopy. The course of the reactions and the identity and homogenity of the products were assessed by one or more of thin layer chromatography (TLC) , high pressure liquid chromatography (HPLC) , or gas-liquid chromatography (GLC) .

The following examples will further illustrate the invention without, however, limiting it thereto. All melting points (m.p.) are given in degrees centigrade (^*C) and are uncorrected.

Example 1 (a)

To a stirred solution of 7.36 ml (84.9 mmol) of chloro- sulfonyl isocyanate in 150 ml of methylene chloride was added benzyl alcohol (8.82 ml, 84.7 mmol) at 0-5°C. After stirring the above solution for 1.5 hours at this temperature, a solution of

15.62 g (93.25 mmol) of 2-amino-pentanoic acid methyl ester hydrochloride in 500 ml of methylene chloride containing triethylamine (25.54 g, 0.2528 mol) was added at 0-5°C, and the resulting mixture was stirred overnight allowing the mixture to warm to room temperature. The reaction mixture was poured into

600 ml of 10% aq. HCl solution, saturated with sodium chloride, and the organic layer was separated. The aqueous layer was

-13- extracted with methylene chloride/ethyl acetate (4:1, 2x200 ml) and the combined organic layer was washed with brine, dried and concentrated in vacuo to yield 28.2 g (87.6%) of 2 - (N- carbobenzvloxvaminosulfonvDaminopentanoic acid methvl ester

(Formula XIV: R=CH3, R¹=H; R²=propyl; R³=H) as a solid, m.p. 76- 78'C.

(b) A solution of 2- ( -carbobenzyloxyaminosulfony1 ) aminopentanoic acid methyl ester (26.7 g) in methanol (200 ml) under nitrogen was cooled to 0°C and 1.5 g of 10% Pd/C was added. The mixture was placed into a Parr Apparatus and hydrogenated for 2 hours. The catalyst was removed on a pad of CELITE® and the filtrate was concentrated in vacuo and purified by flash silica gel chromatography (4 - 6% methanol in methylene chloride) to afford 11.0 g (62%) of 2- (aminosulfonylamino)pentanoic acid methyl ester (Formula VII: R=CH3; R¹=H; R²=propyl; R3=H) as a solid, m.p. 63-64°C.

(c) A solution of 2- (aminosulfonylamino)pentanoic acid methyl ester (10.5 g; 0.05 mmol) in methanol (100 ml) was added to a solution of sodium methoxide (3.78 g, from 1.61 g of Na) in 100 ml of methanol and the resulting reaction mixture was refluxed for 18 hours. The mixture was cooled, neutralized with BIO-RAD® 50W-X8 H⁺ ion exchange resin, and filtered. The filtrate was concentrated in vacuo to yield an oil which was crystallized from methanol/hexane to afford 6.5 g (73%) of 4 -propyl-1.2.5- thiadiazolidin-3-one 1.1-dioxide (Formula IV: R¹=H; R²=propyl; R³=H) .

(d) To a mixture of 4-propyl-l, 2 , 5-thiadiazolidin-3-one 1,1- dioxide (1.0 g, 5.6 mmol) suspended in 15 ml of toluene containing tetrabutylammonium bromide (0.18 g, 0.56 mmol) was added phenylthiomethyl chloride (0.98 g, 6.2^' mmol) and the resulting mixture was refluxed (120°C) for 20 hours. The mixture was cooled, filtered, and the filtrate was concentrated in vacuo. The

-14- residue was purified by silica gel flash column chromatography (20% of ethyl acetate in hexane) to afford 1.16 g of 2 - ohenvlthiomethvl-4-pronvl-l .2.5-thiadiazolidin-3-one 1.1-dioxide (Formula VI: R¹=H; R²=propyl; R³=H) .

(e) To a solution of 2-phenylthiomethyl-4-propyl-1 , 2 , 5- thiadiazolidin-3-one 1,1-dioxide (1.1 g, 3.6 mmol) in 10 ml of methylene chloride was added sulfuryl chloride (0.44 ml, 5.5 mmol) and the mixture was stirred for 3 hours at room temperature. The mixture was concentrated in vacuo, the residue triturated in hexane (50ml) for 1 hour, the resulting solid filtered and purified by silica gel flash column chromatography (20-25% of ethyl acetate in hexane) to afford 0.31 g of 2-chloromethyl-4- propvl-1.2.5-thiadiazolidin-3-one 1.1-dioxide (Formula II: R¹=H; R =propyl; R³=H; x'=Cl) as a solid, m.p. 62-63.5°C.

(f)

The sodium salt of 5-mercapto-l-phenyl-lH-tetrazole (0.42 g)

(Formula III: M⁺=Na⁺; X=S;

) was added to a solution of

2-chloromethyl-4-propyl-l, 2, 5-thiadiazolidin-3-one 1, 1-dioxide (0.44 g) in DMF (10 ml), and the resulting mixture was allowed to react at 50°C for 6 hours and then cooled. The mixture was poured into ice/water, extracted with ethyl acetate, and the organic layer was washed with water and brine, dried, and concentrated in vacuo. The residue was purified by flash chromatography (35% ethyl acetate in hexane) to afford 0.69 g (96%) of 2- (l-phenvl-lH-tetrazol-5-yl-thiomethvl ) -4-oropvl-l.2.5- thiadiazolidin-3-one 1,1-dioxide (Formula I: R!=H; R²=propyl;

R³ =H ; X=S ; R = ^Ph ) as a solid, m . p . 125 . 5 -126 . 5°C . Example 2 (a)

To a stirred solution of 7.36 ml (84.9 mmol) of chloro- sulfonyl isocyanate in 150 ml of methylene chloride was added benzyl alcohol (8.82 ml, 84.7 mmol) at 0°C over a period of 35 minutes. After stirring the above solution for 2 hours at this temperature, a solution of 15.62 g (93.25 mmol) of DL-valine methyl ester hydrochloride in methylene chloride containing triethylamine (36.67 ml) was added at 0-5°C, and the resulting mixture was stirred overnight allowing the mixture to warm to room temperature. The reaction mixture was poured into 600 ml of 10% aq. HCl solution, saturated with sodium chloride, and the organic layer was separated. The aqueous layer was extracted with methylene chloride (2x200 ml) and the combined organic layer was washed with brine, dried, and concentrated in vacuo to yield 30 g of N- (carbobenzyloxyaminosulfonyl) -DL-valine methyl ester (Formula

XIV: R=CH3; R¹=H; R²=isopropyl; R³=H) as a solid.

(b) A solution of N- (carbobenzyloxyaminosulfonyl) -DL-valine methyl ester (28.5 g) in methanol (200 ml) under nitrogen was cooled to 0°C and 1.8 g of 10% Pd/C was added. The mixture was placed into a Parr Apparatus and hydrogenated at 55 psi for 2 hours. The catalyst was removed on a pad of CELITE® and the filtrate was concentrated in vacuo and purified by flash silica gel chromatography (ethyl acetate/hexane, 1:1) to afford 17.2 g (96%) of N- (aminosulfonyl) -DL-valine methyl ester (Formula VII: R=CH3 ; R¹=H; R²=isopropyl; R³=H) as a solid.

(c) A solution of freshly prepared sodium methoxide (6.41 g, from 2.3 g of Na) in 100 ml of methanol was added to a solution of N- (aminosulfonyl) -DL-valine methyl ester (10.5 g; 0.05 mmol) in methanol (150 ml) and the resulting reaction mixture was stirred at room temperature for 6 hours. The mixture was cooled, neutralized with BIO-RAD® 50W-X8 H⁺ ion exchange resin, and filtered. The filtrate was concentrated in vacuo to yield a solid residue which was crystallized from methanol/hexane to afford 16.4 g of a crude 4-isopropvl-l .2.5-thiadiazolidin- -one 1.1-dioxide (Formula IV: R¹=H; R =isopropyl; R³=H) .

(d) To a mixture of 4-isopropyl-l,2, 5-thiadiazolidin-3-one 1,1- dioxide (7.0 g, 39.32 mmol) suspended in 150 ml of toluene was added phenylthiomethyl chloride (6.83 g, 43 mmol) and tetrabutylammonium bromide (1.26 g, 3.93 mmol) . The resulting mixture was refluxed for 17 hours, cooled, filtered, and the filtrate was concentrated in vacuo. The residue was purified by column chromatography to afford 5.2 g of 2-phenylthiomethyl-4- isopropyl-1 , 2.5-thiadiazolidin-3-one 1.1-dioxide (Formula VI: R¹=H; R²=isopropyl; R³=H) .

(e) To a solution of 2-phenylthiomethyl-4-isopropyl-l, 2 , 5- thiadiazolidin-3-one 1,1-dioxide (3.8 g) in 60 ml of methylene chloride was added sulfuryl chloride (1.52 ml) and the mixture was stirred for 2.5 hours at room temperature. The mixture was concentrated in vacuo and the residue triturated in hexane (200 ml) for 2 hours. The resulting solid was filtered and washed with hexane to afford, after drying, 2.7 g (94%) of 2-chloromethyl-4- isopropvl-1.2.5-thiadiazolidin-3-one 1.1-dioxide (Formula II: R¹=H; R =isopropyl; R³=H; x'=Cl) as a solid, m.p. 71-72°C.

(f) The sodium salt of 5-mercapto-l-phenyl-lH-tetrazole (0.48 g)

(Formula III: M⁺=Na⁺; X=S; R = ^Ph ) was added to a solution of

2-chloromethyl-4-isopropyl-l,2, 5-thiadiazolidin-3-one 1, 1-dioxide (0.5 g) in DMF (10 ml), and the resulting mixture was allowed to react at 60°C for 10 hours and then cooled. The mixture was poured into ice/water containing saturated sodium bicarbonate solution, extracted with ethyl acetate, and the organic layer was washed with water and brine, dried, and concentrated in vacuo.

-17- The residue was purified by silica gel chromatography (35% ethyl acetate in hexane) to afford 0.57 g (70%) of 2- ( 1-phenyl-lH- tetrazol-5-vl-thiomethvl)-4-isopropvl-1.2.5-thiadiazolidin-3-one

1.1 -dioxide (Formula I: R¹=H; R²=isopropyl ; R³=H; X=Ξ;

R⁴= ^Ph ) as a solid, m.p.100.5-101.5°C.

Example 3 (a)

A solution of 2- (N-carbobenzyloxysulfonyl)aminopentanoic acid methyl ester (33 g) in methanol (250 ml) under nitrogen was cooled to 0°C and 1.4 g of 10% Pd/C was added. The mixture was placed into a Parr Apparatus and hydrogenated at 55 psi for 2 hours. The catalyst was removed on a pad of CELITE® and the filtrate was concentrated in vacuo and purified by flash silica gel chromatography (50% ethyl acetate in hexane) to afford 13.5 g

(76%) of 2- (aminosulfonvl)aminopentanoic acid methvl ester

(Formula VII: R=CH3; R¹=H; R²=propyl; R³=H) as a solid, m.p. 63-

64'C.

(b) A solution of 2- (aminosulfonyl)aminopentanoic acid methyl ester (13 g; 0.05 mmol) in methanol (150 ml) was added to a solution of sodium methoxide (5.54 g, from 2 g of Na) in 150 ml of methanol and the resulting reaction mixture was refluxed for 18 hours. The mixture was cooled, neutralized with BIO-RAD® 50 -X8 H⁺ ion exchange resin, and filtered. The filtrate was concentrated in vacuo to yield an oil which was crystallized from methanol/hexane to afford 10.8 g (quantitative) of 4-propyl-l.2.5- thiadiazolidin-3-one 1,1-dioxide (Formula IV: R¹=H; R²=propyl; R³=H) .

(c) To a mixture of 4-propyl-l, 2 , 5-thiadiazolidin-3-one 1,1- dioxide (5.0 g, 28.25 mmol) suspended in 150 ml of toluene was added phenylmethyl chloride (5.32 g, 31.03 mmol) and

-18- tetrabutylammonium bromide (0.9 g, 0.28 mmol) . The resulting mixture was refluxed for 19 hours, cooled, filtered, and the filtrate was concentrated in vacuo. The residue was purified by flash chromatography to afford 2.97 g (39%) of 2-phenyl ethv1-4- propvl-1.2. -thiadiazolidin-3-one 1.1-dioxide (Formula IX: R¹=H; R =propyl) as a solid, m.p., 63.5-65.5°C.

(d) Potassium t-butoxide (1.05 g, 9.37 mmol) was added to a solution of 2-phenylmethyl-4-propyl-l, 2, 5-thiadiazolidin-3-one 1,1-dioxide (2.4 g, 8.95 mmol) in 25 ml of THF at 0°C and the mixture was stirred at this temperature for 1 hour. To the mixture was added methyl iodide (6.35 g, 44.73 mmol) and the resulting mixture was allowed to stir at 0°C for 0.5 hour and at room temperature for 4 hours. The resulting mixture was quenched with saturated ammonium chloride, extracted with ethyl acetate and the organic layer was washed with brine. The organic layer was dried, concentrated in vacuo, and the residue was purified by flash chromatography to afford 2.4 g (95%) of 2-phenylmethyl-4- propvl-5-methyl-l .2.5-thiadiazol-idin-3-one 1.1-dioxide (Formula XI: R¹=H; R²=propyl; R³=CH3) as an oil.

(e) To a suspension of 3.5 g of 10% Pd/C in 150 ml of methanol containing ammonium formate (14 g) was added a solution of 2- phenylmethyl-4-propyl-5-methy1-1, 2, 5-thiadiazolidin-3-one 1,1- dioxide (8.7 g) in 40 ml of methanol under nitrogen. The mixture was stirred at room temperature for 15 hours, filtered through a pad of CELITE® and the residue was washed with methanol. The combined filtrate was concentrated in vacuo to afford 7.6 g of ______ propyl- -methyl-1.2.5-thiadiazolidin-3-one 1.1-dioxide (Formula IV: R¹=H; R²=propyl; R³=CH3) as a solid.

(f) A mixture of 4-propyl-5-methyl-l, 2, 5-thiadiazolidin-3-one 1,1-dioxide (9 g) , phenylthiomethyl chloride (7.43 g) and tetrabutylammonium bromide (1 g) was suspended in 200 ml of toluene, refluxed for 8 hours, cooled, and concentrated in vacuo. The residue was purified by flash chromatography (15-20% ethyl acetate in hexane) to afford 8.5 g (88%) of 2-phenylthiomethyl-4- propvl-5-methvl-1.2. - hiadiazolidin- -one 1.1-dioxide (Formula VI: R¹=H; R²=propyl; R³=CH3) as an oil.

(g)

To a solution of 2-phenylthiomethyl-4-propyl-5-methyl-l, 2 , 5- thiadiazolidin-3-one 1,1-dioxide (8.4 g) in 150 ml of methylene chloride was added sulfuryl chloride (3.22 ml) and the mixture was stirred for 3 hours at room temperature. The mixture was concentrated in vacuo and the residue triturated in hexane (150 ml) for 2 hours. The solvent was concentrated in vacuo and the residue was purified by flash chromatography (silica gel) to afford 5.7 g of 2 -chloromethv1 - 4 -proovl - 5 -methv 1 - 1.2.5- thiadiazolidin-3-one 1.1-dioxide (Formula II: R¹=H; R =propyl; R³=CH3; x^'=Cl) as an oil.

(h) A mixture of 2-chloromethyl-4-propy1-5-methyl-l , 2 , 5- thiadiazolidin-3-one 1,1-dioxide (0.5 g; 2.1 mmol) and sodium salt of 5-mercapto-l-phenyl-lH-tetrazole (0.44 g; 2.2 mmol) (Formula

III: M⁺=Na⁺; X=S; R = ^Ph ) in 10 ml of DMF was allowed to react at 60-65°C for 8 hours and then cooled. The mixture was poured into ice/water containing saturated sodium bicarbonate solution, extracted with ether (2x150 ml) , and the organic layer was washed with water and brine, dried, and concentrated in vacuo. The residue was purified by silica gel chromatography (35% ethyl acetate in hexane) to afford 0.62 g (78%) of 2- ( 1-phenyl-lH- tetrazol-5-vl-thiomethvl)-4-propvl-5-methvl-1.2.5-thiadiazolidin-

3-one 1.1-dioxide (Formula I: R¹=H; R²=propyl; R³=CH3; X=S;

R =

Example 4 ( a )

Eight grams (44.94 mmol) of 4-isopropyl-l, 2, 5-thiadiazolidin-

3-one 1,1-dioxide, phenylmethyl bromide (8.09 g, 47.2 mmol), and tetrabutylammonium bromide (1.5 g, 4.66 mmol) were suspended in toluene/DMF (200ml/50ml) and allowed to react at 130°C for 30 hours. The resulting mixture was cooled, the excess toluene was concentrated in vacuo, and the residue was diluted with 200 ml of water and extracted with ether/ethyl acetate (4:1, 700 ml) . The organic layer was washed with water and brine, dried and concentrated in vacuo to yield a residue which was purified by flash chromatography to afford 8.6 g (72%) of 2-phenylmethyl-4- isopropyl-1.2 , 5-thiadiazol-idin-3-one 1.1-dioxide (Formula IX:

R¹=H; R =isopropyl) as a solid.

(b) To a solution of potassium t-butoxide (3.53 g, 29 mmol) in THF was added to a solution of 2-phenylmethy1-4-isopropy1-1 , 2 , 5- thiadiazolidin-3-one 1,1-dioxide (7.7 g, 29 mmol) in THF at 0°C and the mixture was stirred at this temperature for 1 hour. To the mixture was added methyl iodide (20.38 g, 0.143 mol) and the resulting mixture was allowed to stir at room temperature for 2.5 hours. The resulting mixture was quenched with brine, extracted with ether, and the organic layer was washed with brine. The organic layer was dried, concentrated in vacuo, and the residue was purified by flash chromatography to afford 7.1 g (88%) of 2- phenvlmethvl-4-isopropvl-5-methvl-1.2.5-thiadiazolidin-3-one 1.1- dioxide (Formula XI: R¹=H; R²=isopropyl; R³=CH3) as a solid, m.p. 52.5-54'C.

(c) To a suspension of 3.5 g of 10% Pd/C in 150 ml of methanol containing ammonium formate (15 g) was added a solution of 2- phenylmethy1-4-isopropy1-5-methy1-1, 2, 5-thiadiazolidin-3-one 1,1- dioxide (7.1 g) in 50 ml of methanol. The mixture was stirred at room temperature for 7 hours, filtered through a pad of CELITE® and the residue was washed with methanol. The combined filtrate was concentrated in vacuo to afford -isopropyl-5-methyl-1.2,5- thiadiazolidin-3-one 1.1-dioxide 2-ammonium salt (Formula IV: R1=H; R²=isopropyl; R³=CH3; as ammonium salt) .

(d) A mixture of 4-isopropyl-5-methyl-l,2 , 5-thiadiazolidin-3-one 1,1-dioxide 2-ammonium salt (5.26 g, 25.2 mmol) , phenylthiomethyl chloride (5.6 g, 35.3 mmol) and tetrabutylammonium bromide (0.81 g, 2.51 mmol) suspended in 200 ml of toluene/DMF (3:1) was refluxed for 16 hours, cooled, and concentrated in vacuo. The residue was diluted with 150 ml of water, extracted with ether/ethyl acetate (5:1, 600 ml) , and the organic layer was washed with water, brine, and dried. The organic solution was concentrated in vacuo and the residue was purified by flash chromatography to afford 6.47 g (82%) of 2 -phenylthiomethyl-4- isopropvl-5-methvl-l .2. -thiadiazolidin-3-one 1.1-dioxide (Formula VI: R¹=H; R²=isopropyl; R³=CH3) as a solid, m.p. 82-83°C.

(e) To a solution of 2-phenylthiomethyl-4-isopropyl-5-methyl- 1, 2 , 5-thiadiazolidin-3-one 1,1-dioxide (6.38 g, 23.31 mmol) in 150 ml of methylene chloride was added sulfuryl chloride (2.5 ml, 30.4 mmol) and the mixture was stirred for 2 hours at room temperature. The mixture was concentrated in vacuo and the residue triturated in hexane to afford 4.32 g (88%) of 2-chloromethyl-4-isopropyl-5- methvl-1, 2.5-thiadiazolidin-3-one 1.1-dioxide (Formula II: R¹=H; R²=isopropyl; R³=CH3; x'=Cl) as a solid, m.p. 118.5-119.5°C.

(f) To a mixture of 2-chloromethyl-4-isopropyl-5-methyl-l, 2 , 5- thiadiazolidin-3-one 1,1-dioxide (0.5 g; 2.08 mmol) in 10 ml of

DMF was .added sodium salt of 5-mercapto-l-phenyl-lH-tetrazole

(0.46 g; 2.3 mmol) (Formula III:

) at room temperature and the resulting mixture was allowed to react at 80-

90°C for 9 hours and then cooled. The mixture was poured into ice/water containing saturated sodium bicarbonate solution, extracted with ether/ethyl acetate (4:1, 250 ml) , and the organic layer was washed with water and brine, dried, and concentrated in vacuo. The residue was purified by silica gel chromatography (30% ethyl acetate in hexane) to afford 0.68 g (86%) of 2- (1-phenyl-lH- tetrazol-5-vl-thiomethvl) -4-isopropyl-5-methvl-l.2.5- thiadiazolidin-3-one 1.1-dioxide (Formula I: R!=H; R²=isopropyl;

Example 5 (a)

To a stirred solution of 14.72 ml (0.17 mol) of chloro- sulfonyl isocyanate in 400 ml of methylene chloride was added benzyl alcohol (17.69 ml, 0.17 mol) at 0-5°C. After stirring the above solution for 1.5 hours at this temperature, a solution of

31.24 g (0.186 mol) of 2-amino-pentanoic acid methyl ester hydrochloride in 1100 ml of methylene chloride containing triethylamine (51.08 g, 0.5 mol) was added at 0-5°C, and the resulting mixture was stirred overnight allowing the mixture to warm to room temperature. The reaction mixture was poured into

600 ml of 10% aq. HCl solution, saturated with sodium chloride, and the organic layer was separated. The aqueous layer was extracted with methylene chloride/ethyl acetate (4:1) and the combined organic layer was washed with brine, dried and concentrated in vacuo to yield 47.7 g (82%) of 2 - ( N - carbobenzyloxyamino-sulfonyl) aminopentanoic acid methyl ester

(Formula XIV: R=CH3; R¹=H; R²=propyl; R³=H) as a solid, m.p. 76-

78°C.

(b) A mixture of 2- (N-carbobenzyloxyaminosulfonyl) aminopentanoic acid (46.7 g) , methanol (350 mL) and 10% palladium on carbon (3.0 g) was hydrogenated at 55 psi for about 2 hours. The catalyst was removed by filtration through CELITE®, the solvent was removed in vacuo and the residue was purified by column chromatography on silica eluting with 50% ethyl acetate/hexane to afford 25.6 g (90%) of 2- (aminosulfonylamino)oentanoic acid methyl ester (Formula XIV: R=CH3; R¹=H; R²=propyl; R³=H) , m.p. 63-64^*C.

(c) A solution of 2- (aminosulfonylamino)pentanoic acid methyl ester (24.6 g; 0.117 mmol) in methanol (150 ml) was added to a solution of sodium methoxide (8.86 g, from 3.77 g of Na) in 150 ml of methanol and the resulting reaction mixture was refluxed for 18 hours. The mixture was cooled, neutralized with BIO-RAD® 50 -X8 H⁺ ion exchange resin, and filtered. The filtrate was concentrated in vacuo to yield an oil which was crystallized from methanol/hexane to afford 4-propyl-l.2 , 5-thiadiazolidin-3-one 1.1- dioxide (Formula IV: R!=H; R²=propyl; R³=H) .

(d) A mixture of 4-propyl-l,2, 5-thiadiazolidin-3-one 1,1-dioxide

(20.74 g, 0.117 mol), phenylmethyl bromide (22.09 g, 0.129 mol) and tetrabutylammonium bromide (3.77 g, 0.012 mol) suspended in toluene/DMF (400ml:50ml) was refluxed for 40 hours, and cooled. The mixture was poured into ice/water, extracted with ethyl acetate, and the organic layer was concentrated in vacuo. The residue was purified by flash chromatography to afford 11.1 g of 2-phenylmethyl-4-propyl-l.2.5-thiadiazolidin-3-one 1.1-dioxide

(Formula IX: R¹=H; R²=propyl) as a solid.

(e) Potassium t-butoxide (2.3 g, 20.5 mmol) was added to a solution of 2-phenylmethyl-4-propyl-l, 2, -thiadiazolidin-3-one 1,1-dioxide (5 g, 18.6 mmol) in 100 ml of THF at 0°C and the mixture was stirred at this temperature for 1 hour. To the mixture was added ethyl iodide (11.64 g, 74.6 mmol) and the resulting mixture was allowed to stir at room temperature for 40 hours. The resulting mixture was diluted with brine, extracted with ethyl acetate (150 ml) and the organic layer was washed with brine. The organic layer was dried, concentrated in vacuo, and the residue was purified by flash chromatography to afford 5.27 g of 2-phenylmethyl-4-propyl-5-ethyl-l.2.5-thiadiazolidin-3-one 1.1- dioxide (Formula XI: R¹=H; R²=propyl; R³=ethyl) as an oil.

(f) A suspension of 2.0 g of 10% Pd/C in 300 ml of methanol containing ammonium formate (3.35 g) and 2-phenylmethyl-4-propyl- 5-ethyl-l , 2 , 5-thiadiazolidin-3-one 1,1-dioxide (5.25 g) was stirred at room temperature for 20 hours, filtered through a pad of CELITE® and the residue was washed with methanol. The combined filtrate was concentrated in vacuo to afford 3.8 g of 4-propyl-5- ethvl-1.2.5-thiadiazolidin-3-one 1.1-dioxide 2-ammonium salt

(Formula IV: R¹=H; R =propyl; R =ethyl as the ammonium salt) as a solid.

⁽g⁾

A mixture of 4-propyl-5-ethyl-1, 2,5-thiadiazolidin-3-one 1,1- dioxide 2-ammonium salt (3.7 g; 16.6 mmol) , phenylthiomethyl chloride (2.9 g; 18.28 mmol) and tetrabutylammonium bromide (0.53 g) suspended in toluene/DMF (90ml :10ml) was refluxed for 8 hours, cooled, and concentrated in vacuo. The residue was dissolved in water, extracted with ether/ethyl acetate (1:1; 500 ml), the organic layer was washed with water and brine, dried, and concentrated in vacuo. The residue was purified by flash chromatography (15-20% ethyl acetate in hexane) to afford 4.01 g of 2-phenvlthiomethvl-4-propvl-5-ethyl-1.2.5-thiadiazolidin-3-one 1.1-dioxide (Formula VI: R!=H R =propyl; R =ethyl), as an oil.

(h) A mixture of 2-phenylthiomethyl-4-propyl-5-ethyl-l, 2, 5- thiadiazolidin-3-one 1,1-dioxide (3.97 g) and sulfuryl chloride (1.47 ml) in 80 ml of methylene chloride was stirred for 3 hours at room temperature. The mixture was concentrated in vacuo and the residue triturated in hexane. The solvent was concentrated in vacuo and the residue was purified by flash chromatography (silica gel) to afford 2.4 g (77%) of 2-chloromethyl-4-propyl-5-ethyl- l,2.5-thia iazolidin-3-one 1.1-dioxide (Formula II: R^H; R²=propyl; R³=ethyl; x'=Cl) as an oil.

-25- (i) A mixture of 2 -chloromethy 1-4 -propy 1- 5-ethy 1- 1 , 2 , 5 - thiadiazolidin-3-one 1,1-dioxide (0.5 g; 1.96 mmol) and sodium salt of 5-mercapto-l-phenyl-lH-tetrazole (0.39 g; 1.98 mmol)

(Formula III: M⁺=Na⁺;

) in 10 ml of DMF was allowed to react at 80°C for 11 hours and then cooled. The mixture was poured into ice/water containing saturated sodium bicarbonate solution, extracted with ether/ethyl acetate (1:1; 250 ml) , and the organic layer was washed with water and brine, dried, and concentrated in vacuo. The residue was purified by silica gel chromatography (35% ethyl acetate in hexane) to afford 0.56 g (72%) of 2- (l-phenvl-lH-tetrazol-5-vl-thiomethvl) -4-proPvl-5- ethvl-1.2.5-thiadiazolidin-3-one 1.1-dioxide (Formula I: R¹=H;

R²=propyl;

) as an oil.

Example 6 (a)

To a solution of N-t-butoxycarbonyl-sarcosine (50 g; 0.264 mol) in 700 ml of benzene was added 1, 8-diazabicyclo[5.4.0] -undec-

7-ene (DBU; 40.19 g, 0.264 mol) in one portion. To the above clear solution was added 74.84 g (0.528 mol) of methyl iodide in one portion and the resulting clear solution was allowed to reflux for 7 hours. After adding additional methyl iodide (16 ml), the reaction mixture was refluxed with stirring, cooled to room temperature, and stirred overnight. The reaction mixture was filtered, the residue washed with ether, and the combined filtrate was washed with water, saturated sodium bicarbonate solution, and brine. The resulting organic layer was dried over sodium sulfate, filtered, and concentrated in vacuo to afford 46.38 g (86.4 %) of

N-t-butoxvcarbonvl-sarcosine methvl ester as a yellow oil.

-26- (b) A 2 M solution of LDA (70.32 ml, 0.14 mol) was added (via syringe) to a solution of N-t-butoxycarbonyl-sarcosine methyl ester (26 g, 0.1279 mol) in 40 ml of dry THF at -78°C under nitrogen and the mixture was stirred at this temperature for 30 minutes. To the above mixture was added 4-bromo-2-methyl-2-butene (20 g, 0.134 mol) with stirring continuing at -78°C, and the resulting mixture was allowed to warm to room temperature. The reaction mixture was quenched with a saturated ammonium chloride solution at -78°C, and then water was added, and the resulting reaction mixture was extracted with ethyl acetate. The organic layer was washed with water and brine, dried over sodium sulfate, and concentrated in vacuo to yield a yellow oil, which was purified by silica gel column chromatography (20% ethyl acetate in hexane) to afford 22.1 g (63.7 %) of N-t-butoxycarbonyl-2- (3- methvl-2-butenvl)sarcosine methvl ester as an oil.

(c) A solution of N-t-butoxycarbony1-2 - ( 3 -methy1-2 - butenyl)sarcosine methyl ester (22.1 g, 81.44 mmol) in 400 ml of rethanol under nitrogen was cooled to 0°C and 1.5 g of 10% Pd/C was added. The mixture was placed into a Parr Apparatus and hydrogenated for 6 hours. The catalyst was removed on a pad of CELITE® and the filtrate was concentrated in vacuo to afford 22.04 g (99%) of N-t-butoxvcarbonvl-2- (3-methvlbutvl) sarcosine methvl ester as an oil.

(d) A mixture of N-t-butoxycarbonyl-2- (3-methylbutyl)sarcosine methyl ester (22.04 g, 80.62 mmol) in 360 ml of ethereal HCl was stirred at room temperature for 3 days. The resulting mixture was cooled in an ice/bath and then the solvent was concentrated in vacuo to afford after drying 13.17 g (78%) of 2 - ( 3 - methvlbutyl)sarcosine methvl ester hydrochloride (Formula XIII: R=CH3 ; R¹=H; R²= (CH2 ) 2CH (CH3 ) 2 ; R³=CH3; X^~=Cl^") which was recrystallized from methanol/ether, m.p. 110-111°C.

-27- (e) To a stirred solution of 5.77 ml (66.55 mmol) of chloro- sulfonyl isocyanate in methylene chloride was added under nitrogen benzyl alcohol (6.89 ml, 66.55 mmol) at 0-5°C. After stirring the above solution for 1 hour, a solution of 13.166 g (62.78 mmol) of 2- (3-methylbutyl)sarcosine methyl ester hydrochloride in methylene chloride containing triethylamine (27.33 ml, 194.62 mmol) was added at 0-5°C, and the resulting mixture was stirred overnight allowing the mixture to warm to room temperature. The reaction mixture was poured into a 10% aq. HCl solution, saturated with sodium chloride, and the organic layer was separated. The aqueous layer was extracted with methylene chloride and the combined organic layer was washed with brine, dried over magnesium sulfate and concentrated in vacuo to yield 21.22 g (87.2%) of N- (CflrbQbepzvlQxγaminQSUlfQnYl)-2- (3-methylbutyl)sarcosine methyl ester (Formula XIV: R=CH3; R¹=H; R²= (CH2)2CH(CH3) 2; R³=CH3) which was purified by silica column chromatography (20% ethyl acetate in hexane) as an oil.

(f) A solution of (N-carbobenzyloxyaminosulfony1) -2- (3 - methylbutyl)sarcosine methyl ester (20.6 g, 53.17 mmol) in 200 ml of methanol under nitrogen was cooled to 0°C and 1.5 g of 10% Pd/C was added. The mixture was placed into a Parr apparatus and hydrogenated for 3.5 hours. The catalyst was removed on a pad of CELITE® and the filtrate was concentrated in vacuo to afford 13.24 g (98.6%) of N- (aminosul onvl) -2- (3-methvlbutvl) sarcosine methvl ester (Formula VII: R=CH3 ; R¹=H; R²= (CH2) 2CH(CH3) 2; R³=CH3) as an oil.

⁽g⁾

A solution of N- (aminosulfonyl) -2- (3-methylbutyl)sarcosine methyl ester (12.28 g, 48.67 mmol) in methanol (150 ml) was added under nitrogen to a solution of sodium methoxide (Na=2.1 g, 95.71 mmol) in 150 ml of ice-cold methanol. The resulting reaction mixture was stirred at room temperature under nitrogen for 1.5 hours, and the mixture was treated with 25 g of ion-exchange resin

-28- (BIO RAD® 50W-X8 H⁺; 200-400 mesh) for 40 minutes and filtered. The filtrate was concentrated in vacuo to afford 10.7 g (99.8%) of 4-(3-methvlbutvl)-5-methvl-1.2.5-thiadiazolidin-3-one 1.1-dioxide (Formula IV: R¹=H; R²= (CH2 ) 2CH(CH3 ) 2; R³=CH3) as a solid, m.p. 212-214°C.

(h) A mixture of 4- (3-methylbutyl) -5-methyl-l,2, 5-thiadiazolidin- 3-one 1,1-dioxide cesium salt (prepared by reacting 7.7 g (34.95 mmol) of the 1,1-dioxide in methanol with 5.13 g of CS₂CO₃ followed by removal of the solvent) and phenylthiomethyl chloride (6.65 g, 41.94 mmol) suspended in DMF was heated at 85°C for 17 hours. The mixture was cooled, and poured into 300 ml of ice/water. The reaction mixture was extracted with ethyl acetate (3x) and the organic layer was washed with water and brine, and dried over sodium sulfate. The organic layer was concentrated in vacuo and the residue was purified by silica column chromatography (10% ethyl acetate in hexane) to afford 8.15 g (70.6%) of 2 - phenvlthiomethvl-4-(3-methvlbutvl)-5-methvl-1.2.5-thiadiazolidin- 3-one 1.1-dioxide (Formula VI: R¹=H; R²=(CH2)2CH(CH3) 2; R³=CH3) as an oil.

(i) To a solution of 2-phenylthiomethyl-4- (3-methylbutyl) -5- methyl-1,2, 5-thiadiazolidin-3-one 1,1-dioxide (8.15 g, 24.66 mmol) in 200 ml of methylene chloride was added in one portion under nitrogen sulfuryl chloride (2.36 ml, 29.6 mmol) and the mixture was stirred for 3.5 hours at room temperature. The mixture was concentrated in vacuo and the residue was triturated in hexane to afford 4.64 g (70%) of 2-chloromethvl-4- (3-methvlbutvl) -5-methvl-

1.2.5-thiadiazolidin-3-one 1 , 1-djo^j-de (Formula II: R¹=H;

R = (CH2)2CH(CH3)2; R =CH3 x'=Cl) as a solid, m.p. 59-60°C. ⁽j⁾ To a solution of l-phenyl-3-trifluoromethyl-5-hydroxypyrazole

cesium salt (Formula III: M⁺=Cs⁺; X=0;

) (prepared by reaction of the pyrazole (0.34 g, 1.49 mmol) in methanol with CS2CO₃ (0.24 g) followed by removal of the solvent) in 20 ml of DMF was added 2-chloromethyl-4- (3-methylbutyl) -5-methyl-l, 2 , 5- thiadiazolidin-3-one 1,1-dioxide (0.2 g; 0.74 mmol) at room temperature. The resulting solution was allowed to react with stirring at room temperature under nitrogen for 17 hours. The mixture was poured into ice/water, extracted with ethyl acetate (3x50ml) , and the organic layer was washed with water, brine and dried. The organic solvent was concentrated in vacuo and the residue was purified by silica flash column chromatography to afford 180 mg (52%) of 2- (1-phenyl-3-trifluoromethyl-pyrazol-5- vloxvmethvl)-4-(3-methvlbutvl)-5-methvl-1.2.5-thiadiazolidin-3-one 1.1-dioxide (Formula I: R^H R²= (CH2 ) 2CH (CH3 ) 2 ; R³=CH3; X=0;

) as a solid, m.p. 76-77°C.

Example 7 (a)

Following a procedure similar to that described in example

6(b) , but substituting 2.1 equivalents of methyl iodide for 4- bromo-2-methyl-2-butene and utilizing 2.2 equivalents of lithium diisopropyl amide (LDA) it is contemplated that there can be prepared a compound of the formula: (CH3) 2C(CO2CH3)N(CH3) (C02tBu) .

(b) Following a procedure similar to that described in example 6(d) , but substituting the compound of example 7(a) for the compound of example 6(c), it is contemplated that there can be prepared a compound of the formula: (CH3) 2C (C02CH3)NH (CH3 ) -HCl. Following procedures similar to those described in Examples 1(a) -(c) but substituting an appropriate α-amino acid ester of the formula XIII for norvaline methyl ester hydrochloride in example 1(a), it is contemplated that there can be prepared the following compounds of the formula IV illustrated in Table I.

Table I

IV

Example No. Rl R2 R3 Ester Used

8 CH₃ CH₃ CH₃ (CH3)2C(NHCH3)CO2CH •HCl

9 CH2Ph H H C6H5CH2CH(NH2)CO2CH ^•HCl

Following a procedure similar to that described in Example 1(d) but substituting an appropriate compound of the Formula IV for 4-propyl-l, 2 , 5-thiadiazolidin-3-one 1,1-dioxide it is contemplated that there can be prepared the following compounds of the formula VI illustrated in Table II:

Table II

VI

Following a procedure similar to that described in Example 1(e), but substituting an appropriate compound of the formula VI for 2-phenylthiomethyl-4-propyl-l, 2, 5-thiadiazolidin-3-one 1,1- dioxide, it is contemplated that there can be prepared the following compounds of the formula II illustrated in table III:

Table III

II

Following a procedure similar to that described in example 1(f), but substituting an appropriate compound of the formula II for 2-chloromethyl-4-propyl-1,2, 5-thiadiazolidin-3-one 1, 1-dioxide and, if applicable, an appropriate compound of the formula III for the sodium salt of 1-phenyl-5-mercaptotetrazole , it is contemplated thate there can be prepared the following compounds of the formula I illustrated in Table IV:

Table IV

-32 -

Example 18 (a) To a stirred solution of 7.36 ml (85 mmol) of chlorosulfonyl isocyanate in 180 ml of methylene chloride was added phenylmethanol (8.82 ml, 85 mmol) at 0°C over a period of 35 minutes. After stirring the above solution for 2 hours at this temperature, a solution of 16.65 g (93 mmol) of 2- piperidinecarboxylic acid methyl ester hydrochloride in methylene chloride (500 ml) containing triethylamine (35.3 ml) was added at 0-5°C, and the resulting mixture was stirred overnight allowing the mixture to warm to room temperature. The reaction mixture was poured into 600 ml of 10% aq. HCl solution, saturated with sodium chloride, and the organic layer was separated. The aqueous layer was extracted with methylene chloride ( 2x200 ml) and the combined organic layer was washed with brine, dried and concentrated in vacuo to yield 31 g of N- (carbobenzyloxyaminosulfonyl) -2 - pjperidinecarboxylic acid methyl ester(Formula XIV: R = CH3; R¹=H; R² and R³ together = -(CH2)4~) as a solid.

-33- (b) A solution of N- (carbobenzyloxyaminosulfonyl) -2-piperidine- carboxylic acid methyl ester (29.8 g) in methanol (300 ml) under nitrogen was cooled to 0°C and 1.8 g of 10% Pd/C was added. The mixture was placed into a Parr Apparatus and hydrogenated for 2 hours at 55 psi. The catalyst was removed on a pad of CELITE® and the filtrate was concentrated in vacuo and purified by flash silica gel chromatography (35-40% ethyl acetate/hexane) to afford 17 g (90%) of N- (aminosulfonvl) -2-pjperidinecarboxvlic acid methvl ester (Formula VII: R=CH3; Rl=H; R² and R³ together = -(CH2)4-) as a solid, m.p. 72-74°C.

(c)

To a solution of freshly prepared sodium methoxide (6.05 g, from 2.1 g of Na) in 150 ml of methanol was added a solution of N- (aminosulfonyl) -2-piperidinecarboxylic acid methyl ester (15 g; 0.067 mmol) in methanol (100 ml) and the resulting reaction mixture was stirred at room temperature for 2 hours. The mixture was cooled, neutralized with BIO-RAD® 50W-X8 H⁺ ion exchange resin, and filtered. The filtrate was concentrated in vacuo to afford 14.4 g of 1.2.5-thiadiazolor2.3-a13.3a.4.5.6.7- hexahvdropvridine-3-one 1.1-dioxide (Formula IV: R¹=H; R² and R³ together = -(CH2)4~).

(d)

To a mixture of 1, 2 , 5-thiadiazolo[2 , 3-a] 3 , 3a, 4, 5, 6 , 7- hexahydropyridine-3-one 1,1-dioxide (10.0 g, 52.6 mmol) suspended in 400 ml of toluene was added phenylthiomethyl chloride (10.85 g, 68.4 mmol) and tetrabutylammonium bromide (1.69 g) . The resulting mixture was refluxed for 6 hours, cooled, filtered, and the filtrate was concentrated in vacuo. The residue was purified by flash column chromatography (25% ethyl acetate in hexane) to afford 12.83 g (78%) of 2-phenylthiomethyl-l.2.5-thiadiazolof2.3- al 3.3a.4.5.6.7-hexahvdropyridine-3-one 1.1-dioxide (Formula VI: R¹=H; R² and R³ together = -(CH2 ) 4~) as an oil.

-34- (e) To a solution of 2-phenylthiomethyl-l, 2, 5-thiadiazolo[2 , 3- a] 3 , 3a, 4 , 5, 6,7-hexahydropyridine-3-one 1,1-dioxide (12 g) in 250 ml of methylene chloride was added sulfuryl chloride (4.63 ml) and the mixture was stirred for 3 hours at room temperature. The mixture was concentrated in vacuo, the residue triturated in hexane (200ml) for 2 hours, the resulting solid filtered and washed with hexane to afford, after drying, 8.1 g (88%) of ______ chloromethvl-1.2.5-thiadiazolo \ 2 .3-al 3.3a.4.5.6.7- hexahvdroPyridine-3-one 1 , 1-dioxide (Formula II: X'=C1; R!=H R² and R³ together = -(CH2)4~)as a solid, m.p. 124-125.5°C.

(f) The Na salt of l-phenyl-5-mercapto-lH-tetrazole (0.46 g) and 2-chloromethyl-l,2, 5-thiadiazolo[2,3-a]-3,3a,4,5,6,7- hexahydropyridine-3-one 1,1-dioxide (0.5 g) in DMF (10 ml) was stirred at room temperature, and the mixture was allowed to react at 60°C for 6 hours and then cooled. The mixture was poured into ice/water containing saturated sodium bicarbonate, extracted with ethyl acetate/methylene chloride (200 ml; 4:1), and the organic layer was washed with water, brine,, and dried over sodium sulfate. The solvent was concentrated in vacuo and the residue was purified by silica gel flash chromatography (35% ethyl acetate/hexane) to afford 0.6 g (76%) of 2- (l-phenyl-lH-tetrazol-5-yl-thiomethyl ) - 1.2.5-thiadiazolor2.3-a1 . a.4.5.6.7-hexahvdropvridine-3-one 1.1- dioxide (Formula I: R⁴=2- (l-phenyl-lH-tetrazol-5-yl; X=S; R¹=H; R² and R³ together = -(CH2)4~) as a solid, m.p.124-125°C.

Example 19 (a) To a stirred solution of 7.36 ml (84.8 mmol) of chlorosulfonyl isocyanate in 180 ml of methylene chloride was added phenylmethanol (8.82 ml, 84.9 mmol) at 0°C over a period of 35 minutes. After stirring the above solution for 2 hours at this temperture, a solution of 15.54 g (93.28 mmol) of L-proline methyl ester hydrochloride in 500 ml of methylene chloride containing

-35- triethylamine (35.5 ml) was added at 0-5°C, and the resulting mixture was stirred overnight allowing the mixture to warm to room temperature. The reaction mixture was poured into 600 ml of 10% aq. HCl solution, saturated with sodium chloride, and the organic layer was separated. The aqueous layer was extracted with methylene chloride ( 2x200 ml) and the combined organic layer was washed with brine, dried and concentrated in vacuo to yield 31 g of N- (carbobenzvloxvaminosulfonvl)-L-proline methvl ester(Formula XIV: R=CH3; R!=H; R² and R³ together = -(CH2)3~) as an oil.

(b)

A solution of (N-carbobenzyloxyaminosulfony1) -L-proline methyl ester (29 g) in methanol (200 ml) under nitrogen was cooled to 0°C and 1.7 g of 10% Pd/C was added. The mixture was placed into a Parr Apparatus and hydrogenated for 2 hours at 50 psi. The catalyst was removed on a pad of CELITE® and the filtrate was concentrated in vacuo to afford, after crystallization from methanol, 10.85 g of N- (aminosulfonvl) -L-proline methyl es er

(Formula VII: R=CH3 ; R!=H; R² and R³ together = -(CH2)3- ) as a solid.

(c)

To a solution of freshly prepared sodium methoxide (4.3 g, from 1.54 g of Na) in 150 ml of methanol was added a solution of N- (aminosulfonyl) -L-proline methyl ester (10 g; 0.067 mmol) in methanol (200 ml) and the resulting reaction mixture was heated at 70°C for 4 hours. The mixture was cooled, neutralized with BIO- RAD® 50 -X8 H⁺ ion exchange resin, and filtered. The filtrate was concentrated in vacuo to afford 6.0 g of tetrahvdropyrrolof1, 2-bl - 1.2, 5-thiadiazol-3 (2H)one 1.1-dioxide (Formula IV: R¹=H; R² and R³ together = -(CH2)3~) as a solid.

(d)

To a mixture of tetrahydropyrrolo[1, 2-b] -1, 2, 5-thiadiazol- 3(2H)-one 1,1-dioxide (5.0 g, 28.4 mmol) -suspended in 150 ml of toluene was added phenylthiomethyl chloride (6.76 g, 42.6 mmol) and tetrabutylammonium bromide (0.91 g) . The resulting mixture was refluxed for 6 hours, cooled, filtered, and the filtrate was concentrated in vacuo. The residue was purified by flash column

-36- chromatography (25-30% ethyl acetate in hexane) to afford 5.58 g (66%) of 2-phenylthiomethyl-tetrahvdropyrrolo ri.2-b1-1.2,5- thiadiazol-3 (2H) -one 1.1-dioxide (Formula VI: Rl=H; R² and R³ together = -(CH2>3- ) as a solid, m.p. 90.5-91.5°C.

(e) To a solution of 2-phenylthiomethyltetrahydropyrrolo[1, 2-b] - 1, 2, 5-thiadiazol-3 (2H) -one 1,1-dioxide (5 g) in 130 ml of methylene chloride was added sulfuryl chloride (2.02 ml) and the mixture was stirred for 2 hours at room temperature. The mixture was concentrated in vacuo, the residue triturated in hexane (2x, 150 ml, 75 ml) with stirring, the solvent decanted, and the resulting solid filtered and dried to afford 2.96 g (92%) of ______ chloromethyl-tetrahvdropyrrolof1.2-bl -1.2.5-thiadiazol-3 (2H) -one 1.1-dioxide (Formula II: X'=C1; R!=H; R² and R³ together = -(CH2)3- )as a solid, m.p. 46.5-47.5°C.

(f) The Na salt of l-phenyl-5-mercapto-lH-tetrazole (0.57 g) was added to a solution of 2-chloromethyl-tetrahvdroPyrrolof1.2-bl - 1,2, 5-thiadiazol-3 (2H) -one 1, 1-dioxide (0.5 g) in DMF (10 ml) at room temperature, and the mixture was allowed to react at 60°C for 6 hours and then cooled. The mixture was poured into ice/water containing saturated sodium bicarbonate, extracted with ethyl acetate, and the organic layer was washed with water, brine, and dried over sodium sulfate. The solvent was concentrated in vacuo and the residue was purified by silica gel flash chromatography (40% ethyl acetate/hexane) to afford 0.69 g of 2- (1-phenyl-lH- tetrazol-5-vl-thiomethvl)tetrahvdropvrrolori.2-b1 -1.2.5- thiadiazol-3 (2H) -one 1.1-dioxide (Formula I: R =l-pheny1-1H- tetrazol-5-yl; X=S; R¹=H; R² and R³ together = -(CH2)3~) as a solid, m.p.99.5-100.5°C.

-37- Biological Test Results

Representative examples of the compounds of the invention have been found to possess valuable pharmacological properties. In particular, they have been found to inhibit the activity of serine proteases, specifically human leukocyte elastase, and are thus useful in the treatment of degenerative disease conditions such as emphysema, rheumatoid arthritis, pancreatitis, cystic fibrosis, chronic bronchitis, adult respiratory distress syndrome, inflammatory bowel disease, psoriasis, bullouε pemphigoid, periodontal disease, and alpha-1-antitrypsin deficiency.

The pharmacological properties of representative examples of the compounds of the invention were demonstrated by the following conventional in vitro biological test procedure.

The test compound (inhibitor) is dissolved in DMSO in a vial to produce an inhibitor stock solution which has a concentration in the range of 200-1000μM. The inhibitor stock solution is diluted (1:4, 1:16 and 1:64) into assay vials (vials 1, 2 and 3 respectively) containing 2.4 mL of buffer solution (50 mM N-[2- hydroxyethyl] piperazine-N' - [2-ethanesulfonic acid] /NaOH, 500 mM NaCl, pH 7.8 at 25^*C) and DMSO is added so that the total volume in each vial is 3.2 mL. 70 μL, 50 μL, 35 μL and 25 μL of inhibitor from assay vial 1 is placed into the first four wells of a 96-well microtiter plate and each well is made up to 90 μL total volume with the addition of a 25% DMSO/buffer solution. The inhibitor from assay vials 2 and 3 is processed in a similar manner and placed in wells 5-12 respectively to afford a total of 12 different inhibitor concentrations. Four wells (wells 13-16) containing 90 μL of the 25% DMSO/buffer solution but no inhibitor are also run simultaneously with the inhibited wells as a control. 150 μL of substrate solution (prepared by the addition of 500 μL of the human leukocyte elastase (HLE) substrate MeOSuc-Ala-Ala- Pro-Val-pNA (18.7 mM in DMSO) to 19.5 mL of buffer solution) is then added simultaneously into each of the 16 wells and the solution in each well was thoroughly mixed. The 96-well microtiter plate is placed into a Microplate Reader #89815A spectrophotometer and 110 μL of the enzyme solution

(prepared as follows: a mixture of 20 mL of buffer solution and 20 mg of bovine serum albumen is gently vortexed in a scintillation vial and 5 μL HLE stock solution (1 mg/mL dissolved in deionized water) is added) is added simultaneously to each of the 16 wells. Each of the solutions in the wells is throughly mixed and then the time-dependent absorbance data is collected at an absorbance of 410 nM until the assay is complete. It should be noted that although this assay method can be done manually, it is preferred to perform the assay robotically using a Hewlett Packard MicroAssay System Robot .

A plot of the absorbance versus time data thus obtained affords progress curves the final slope of which is equal to the final steady-state velocities (Vp) • Using the program ENZFITTER

(Elsevier software) , the progress curves for the four control assays ([I]=0) are fit by linear regression to yield the enzyme reaction velocity values in the absences of inhibitor (Vo) which are averaged to produce a single fixed value. The inhibition constant Ki (nM) is then obtained from a plot of ril versus V₀/VF

1-Vp/Vo which affords a linear plot wherein: slope =Kj ( 1 +_I§L V Km and [S] is the concentration of the substrate and Km is the Michaelis constant.

Table V summarizes the results obtained from the testing of representative compounds of the invention for human leukocyte elastase inhibitory activity. Tabl e V

The compounds of the invention can be prepared for pharmaceutical use by conventional pharmaceutical procedures that are well known in the art; that is, by formulating a pharmaceutical composition which comprises compounds of the invention or their pharmaceutically acceptable salts together with one or more physiologically acceptable carriers, adjuvants, diluents or vehicles, for oral administration in solid or liquid form, parenteral administration, topical administration or aerosol inhalation administration, and the like.

Solid compositions for oral administration include compressed tablets, pills, powders and granules. In such solid compositions, the active compound is admixed with at least one inert diluent such as starch, calcium carbonate, sucrose or lactose. These compositions may also contain additional substances other than inert diluents, e.g. , lubricating agents, such as magnesium stearate, talc and the like.

Liquid compositions for oral administration include pharmaceutically acceptable emulsions, solutions, suspensions, syrups and elixirs containing inert diluents commonly used in the art, such as water and liquid paraffin. Besides inert diluents such compositions may also contain adjuvants, such as wetting and suspending agents, and sweetening, flavoring, perfuming and preservinα agents. According to the invention, the compounds for oral ac tiiiiisti it ion also include capsules cf absorbable mar<^■■--. ^~.l ,

-40- such as gelatin, containing said active component with or without the addition of diluents or excipients.

Preparations according to the invention for parenteral administration include sterile aqueous, aqueous-organic, and organic solutions, suspensions and emulsions. Examples of organic solvents or suspending media are propylene glycol, polyethylene glycol, vegetable oils such as olive oil and injectable organic esters such as ethyl oleate. These compositions can also contain adjuvants such as stabilizing, preserving, wetting, emulsifying and dispersing agents.

Preparations according to the invention for topical administration or aerosol inhalation administration include dissolving or suspending a compound of the invention in a pharmaceutically acceptable vehicle such as water, aqueous alcohol, glycol, oil solution or oil-water emulsion, and the like.

If desired, the compounds of the invention can further be incorporated into slow release or targeted delivery systems such as polymer matrices, liposomes, and microspheres.

The percentage of active component in such compositions may be varied so that a suitable dosage is obtained. The dosage administered to a particular patient is variable depending upon the clinician's judgment using as criteria: The route of administration, the duration of treatment, the size and physical condition of the patient, the potency of the active component and the patient's response thereto. An effective dosage amount of the active component can thus readily be determined by the clinician after a consideration of all criteria and using his best judgment on the patient's behalf.

Claims

We claim :

A compound of the formula :

wherein R^ is hydrogen, lower-alkyl, or phenyl-lower-alkyl; R² is hydrogen, lower-alkyl, or phenyl-lower-alkyl; R³ is hydrogen, or lower-alkyl; or R² and R³ together are -(CH2)n~ wherein n is 3 or 4;

X is O or S; and R⁴ is a heterocycle selected from the group consisting of tetrazolyl, pyrazolyl, imidazolyl, thiadiazolyl, thiazolyl, and triazolyl which is attached through any available carbon atom thereof to the -X- group (or said heterocycle substituted on any available carbon atom thereof by lower-alkyl, or trihalomethyl; and/or on any available nitrogen atom thereof by lower-alkyl, or phenyl); or a pharmaceutically acceptable acid- addition salt thereof; or where applicable, an enantiomer or a racemic mixture thereof.

2. A compound according to claim 1 wherein R⁴ is a heterocycle selected from the group consisting of tetrazolyl and pyrazolyl (or said heterocycle substituted on any available carbon atom thereof by trihalomethyl; and/or on any available atom thereof by phenyl) .

3. A compound according to claim 2 wherein R^ is hydrogen or lower-alkyl; R² is hydrogen, or lower-alkyl; and R³ is hydrogen or lower-alkyl; or R² and R³ together are -(CH2)n^_-

4. A compound according to claim 3 wherein R⁴ is a heterocycle selected from the group consisting of 5-tetrazolyl and 5-pyrazolyl (or said heterocycle substituted on any available carbon atom

-42- thereof by trifluoromethyl; and/or any available nitrogen atom thereof by phenyl) .

5. A compound according to claim 4 wherein R^- is hydrogen, propyl, isopropyl, or 3-methylbutyl; R² is hydrogen, propyl, isopropyl, or 3-methylbutyl; and R³ is hydrogen, methyl or ethyl; or R² and R³ together are -(CH2)n~-

6. 2- (l-Phenyl-lH-tetrazol-5-yl-thiomethyl-4-propyl-5-methyl- 1, 2, 5-thiadiazolidin-3-one 1,1-dioxide according to claim 5.

7. 2- (l-Phenylpyrazol-5-yl-oxymethyl) -4- (3-methylbutyl) -5- methyl-1, 2, 5-thiadiazolidin-3-one 1,1-dioxide according to claim 5.

8. A pharmaceutical composition for the treatment of degenerative diseases which comprises a pharmaceutically acceptable carrier, adjuvant, diluent or vehicle together with an effective proteolytic enzyme inhibiting amount of a compound according to claim 1.

9. A pharmaceutical composition for the treatment of degenerative diseases which comprises a pharmaceutically acceptable carrier, adjuvant, diluent or vehicle together with an effective proteolytic enzyme inhibiting amount of a compound according to claim 2.

10. A pharmaceutical composition for the treatment of degenerative diseases which comprises a pharmaceutically acceptable carrier, adjuvant, diluent or vehicle together with an effective proteolytic enzyme inhibiting amount of a compound according to claim 3.

11. A pharmaceutical composition for the treatment of degenerative diseases which comprises a pharmaceutically acceptable carrier, adjuvant, diluent or vehicle together with an effective proteolytic enzyme inhibiting amount of a compound according to claim 4.

12. A pharmaceutical composition for the treatment of degenerative diseases which comprises a pharmaceutically acceptable carrier, adjuvant, diluent or vehicle together with an effective proteolytic enzyme inhibiting amount of a compound according to claim 5.

13. A pharmaceutical composition for the treatment of degenerative diseases which comprises a pharmaceutically acceptable carrier, adjuvant, diluent or vehicle together with an effective proteolytic enzyme inhibiting amount of a compound according to claim 6.

14. A pharmaceutical composition for the treatment of degenerative diseases which comprises a pharmaceutically acceptable carrier, adjuvant, diluent or vehicle together with an effective proteolytic enzyme inhibiting amount of a compound according to claim 7.

15. A method for the treatment of degenerative diseases which comprises administering to a patient in need of such treatment an effective proteolytic enzyme inhibiting amount of a compound according to claim 1.

16. A method for the treatment of degenerative diseases which comprises administering to a patient in need of such treatment an effective proteolytic enzyme inhibiting amount of a compound according to claim 2.

17. A method for the treatment of degenerative diseases which comprises administering to a patient in need of such treatment an effective proteolytic enzyme inhibiting amount of a compound according to claim 3.

^•44-

18. A method for the treatment of degenerative diseases which comprises administering to a patient in need of such treatment an effective proteolytic enzyme inhibiting amount of a compound according to claim 4.

19. A method for the treatment of degenerative diseases which comprises administering to a patient in need of such treatment an effective proteolytic enzyme inhibiting amount of a compound according to claim 5.

20. A method for the treatment of degenerative diseases which comprises administering to a patient in need of such treatment an effective proteolytic enzyme inhibiting amount of a compound according to claim 6.

21. A method for the treatment of degenerative diseases which comprises administering to a patient in need of such treatment an effective proteolytic enzyme inhibiting amount of a compound according to claim 7.

22. A method according to claim 15 wherein said degenerative diseases are selected from emphysema, rheumatoid arthritis, pancreatitis, cystic fibrosis, chronic bronchitis, adult respiratory distress syndrome, inflammatory bowel disease, psoriasis, bullous pemphigoid, periodontal disease, and alpha-1- antitrypsin deficiency.

23. A method according to claim 22 wherein said degenerative diseases are selected from emphysema, cystic fibrosis, chronic bronchitis, and adult respiratory distress syndrome.