NZ750323B2 - 2-aminopyrimidine derivatives for the treatment of viral infections - Google Patents

Abstract

The present invention provides method of making a compound of formula (I) or a pharmaceutically acceptable salt thereof, wherein in formula (I) X represents S, S=O or O=S=O, R1 is hydrogen, straight-chain or branched-chain (C1-6)-alkyl, (C1-6)-alkoxy or aryl, R2 is straight-chain or branched-chain (C1-3)-alkyl or (C3-6)-cycloalkyl and n = 1 or 2; the method comprising: (1) reacting a compound of formula A-1, or a hydrochloride salt thereof, with a base and a compound of formula B-1 to form a compound of formula (I) wherein X represents S; the method optionally further comprising: (2-a) reacting the compound of formula (I) wherein X represents S with sodium periodate to form a compound of formula (I) wherein X represents S=O; or (2-b) reacting the compound of formula (I) wherein X represents S with oxone to form a compound of formula (I) wherein X represents O=S=O. n (C1-3)-alkyl or (C3-6)-cycloalkyl and n = 1 or 2; the method comprising: (1) reacting a compound of formula A-1, or a hydrochloride salt thereof, with a base and a compound of formula B-1 to form a compound of formula (I) wherein X represents S; the method optionally further comprising: (2-a) reacting the compound of formula (I) wherein X represents S with sodium periodate to form a compound of formula (I) wherein X represents S=O; or (2-b) reacting the compound of formula (I) wherein X represents S with oxone to form a compound of formula (I) wherein X represents O=S=O.

Description

-AMINOPYRIMIDINE DERIVATIVES FOR THE TREATMENT OF VIRAL INFECTIONS This invention s to 2-aminopyrimidine derivatives, ses for their preparation, pharmaceutical compositions, and their use in ng viral infections.

The present invention relates to the use of 2-aminopyrimidine derivatives in the treatment of viral infections, immune or inflammatory disorders, whereby the modulation, or agonism, of toll-like-receptors (TLRs) is involved. Toll-Like Receptors are primary transmembrane proteins characterized by an extracellular leucine rich domain and a cytoplasmic extension that contains a conserved region. The innate immune system can recognize pathogen- associated molecular patterns via these TLRs expressed on the cell surface of certain types of immune cells. Recognition of foreign pathogens activates the production of cytokines and upregulation of co-stimulatory molecules on phagocytes. This leads to the modulation of T cell behaviour.

It has been estimated that most ian species have between ten and n types of Toll—like ors. en TLRs (named TLR1 to TLR13) have been identified in humans and mice together, and lent forms of many of these have been found in other mammalian species. However, equivalents of certain TLR found in humans are not present in all mammals. For example, a gene coding for a protein analogous to TLR10 in humans is present in mice, but s to have been damaged at some point in the past by a retrovirus.

On the other hand, mice express TLRs 11, 12, and 13, none of which are represented in humans. Other mammals may express TLRs which are not found in humans. Other non-mammalian species may have TLRs distinct from mammals, as demonstrated by TLR14, which is found in the Takifugu pufferfish. This may complicate the process of using experimental animals as models of human innate immunity.

For reviews on TLRs see the ing journal articles. Hoffmann, J.A., Nature, 426, p33—38, 2003; Akira, S., Takeda, K., and Kaisho, T., Annual Rev.

Immunology, 21, p335-376, 2003; Ulevitch, R. J., Nature Reviews: Immunology, 4, p512-520, 2004.

Compounds indicating activity on Toll-Like receptors have been previously described such as purine derivatives in WO 17670, adenine derivatives in WO 98/01448 and WO 99/28321, and pyrimidines in .

However, there exists a strong need for novel Toll-Like receptor modulators having red selectivity, higher potency, higher metabolic ity, and an improved safety profile compared to the compounds of the prior art.

In one aspect of the invention, there is provided a method of making a compound of formula (I) or a pharmaceutically acceptable salt thereof, n X represents S, S=O or O=S=O, R1 is hydrogen, straight-chain or branched-chain (C1-6)-alkyl, (C1-6)-alkoxy or aryl, R2 is straight-chain or branched-chain (C1-3)-alkyl or (C3-6)-cycloalkyl and n = 1 or 2; the method sing: (1) reacting a compound of formula A-1: (A-1), or a hydrochloride salt thereof, with a base and a compound of formula B-1: (B-1) to form a compound of formula (I) wherein X represents S; [FOLLOWED BY PAGE 2a] - 2a - the method optionally further comprising: (2-a) reacting the compound of formula (I) wherein X represents S with sodium periodate to form a compound of formula (I) wherein X represents S=O; (2-b) reacting the compound of a (I) wherein X represents S with oxone to form a compound of formula (I) wherein X represents O=S=O.

In accordance with the present invention a nd of a (I) is provided or a pharmaceutically acceptable salt, tautomer(s), stereo-isomeric forms, solvate or polymorph thereof, wherein X represents S, S=O or O=S=O, R1 is hydrogen, (C1-6)-alkyl, (C1-6)-alkoxy or aryl, R2 is (C1-3)-alkyl or (C3-6)-cycloalkyl and n = 1 or 2.

The compounds of formula (I) and their pharmaceutically acceptable salts, tautomer(s), -isomeric forms, solvate or polymorph thereof have activity as pharmaceuticals, in ular as modulators of Toll-Like ors (especially TLR7 and/or TLR8 activity).

In a further aspect the present invention provides a pharmaceutical ition comprising a compound of formula (I) or a pharmaceutically acceptable salt, tautomer, stereo-isomeric form, solvate or polymorph thereof together with one or more pharmaceutically acceptable excipients, diluents or carriers.

Furthermore a compound of formula (I) or a pharmaceutically acceptable salt, solvate, er, stereo-isomeric form or polymorph f according to the current invention, or a pharmaceutical composition sing said compound of formula(I) or a pharmaceutically acceptable salt, solvate, tautomer, stereoisomeric form or polymorph thereof can be used as a medicament.

[FOLLOWED BY PAGE 3] 2014/053273 Another aspect of the invention is that a compound of formula (I) or its pharmaceutically acceptable salt, solvate, tautomer, stereo-isomeric form or polymorph thereof, or said pharmaceutical ition comprising said compound of formula (I) or a pharmaceutically acceptable salt, solvate, tautomer, stereo—isomeric form or polymorph thereof can be used accordingly in the treatment of a disorder where the modulation of TLR’s, more specifically TLR7 and /or TLR8, is involved.

The term )-alkyl" or "(C1_3)-alkyl refers to a straight-chain, branched-chain or cyclic saturated aliphatic hydrocarbon containing the specified number of carbon atoms.

The term "aryl" means an aromatic ring structure ally comprising one or two heteroatoms selected from N, O and S, in particular from N and O. Said aromatic ring structure may have 4, 5, 6 or 7 ring atoms. In particular, said aromatic ring structure may have 5 or 6 ring atoms.

The term "(C1_6)-alkoxy refers to an alkyl (carbon and hydrogen chain) group singular bonded to oxygen like for ce a methoxy group or ethoxy group.

The term "(Cs-e)-cycloalkyl" means refers to a carbocyclic ring containing the specified number of carbon atoms.

As used herein, any chemical formula with bonds shown only as solid lines and not as solid wedged or hashed wedged bonds, or otherwise indicated as having a particular configuration (e.g. R, 8) around one or more atoms, contemplates each possible stereoisomer, or mixture of two or more stereoisomers.

The terms oisomers", "stereoisomeric forms" or "stereochemically isomeric forms" hereinbefore or hereinafter are used interchangeably.

The invention includes all stereoisomers of the compounds of the invention either as a pure stereoisomer or as a mixture of two or more stereoisomers. omers are stereoisomers that are non—superimposable mirror images of each other. A 1:1 mixture of a pair of enantiomers is a racemate or racemic mixture.

Diastereomers (or diastereoisomers) are stereoisomers that are not enantiomers, i.e. they are not related as mirror images. If a compound ns a double bond, the substituents may be in the E or the Z uration. If a compound contains an at least tituted non-aromatic cyclic group, the tuents may be in the cis or trans configuration.

Therefore, the invention es enantiomers, diastereomers, racemates, E isomers, Z isomers, cis isomers, trans isomers and mixtures thereof, whenever chemically possible.

The meaning of all those terms, i.e. omers, diastereomers, racemates, E isomers, Z isomers, cis isomers, trans isomers and mixtures thereof are known to the skilled person.

The absolute configuration is specified according to the Cahn-lngold-Prelog system. The configuration at an asymmetric atom is ied by either R or 8.

Resolved stereoisomers whose absolute configuration is not known can be designated by (+) or (-) depending on the direction in which they rotate plane zed light. For instance, ed enantiomers whose te configuration is not known can be designated by (+) or (-) depending on the direction in which they rotate plane polarized light.

When a specific stereoisomer is fied, this means that said stereoisomer is substantially free, i.e. associated with less than 50%, preferably less than 20%, more preferably less than 10%, even more preferably less than 5%, in particular less than 2% and most ably less than 1%, of the other stereoisomers. Thus, when a compound of Formula (I) is for instance specified as (R), this means that the nd is substantially free of the (S) isomer; when a compound of Formula (I) is for instance specified as E, this means that the compound is substantially free of the Z isomer; when a compound of Formula (I) is for instance specified as cis, this means that the compound is substantially free of the trans isomer.

Pharmaceutically acceptable salts of the nds of formula (l) include the acid addition and base salts thereof. Suitable acid addition salts are formed from acids which form non-toxic salts. Suitable base salts are formed from bases which form non-toxic salts.

The compounds of the invention may also exist in ated and solvated forms. The term "solvate" is used herein to describe a molecular complex comprising the compound of the invention and one or more pharmaceutically acceptable solvent molecules, for e, ethanol.

The term "polymorph" refers to the ability of the compound of the invention to exist in more than one form or crystal structure.

The compounds of the present invention may be administered as lline or amorphous products. They may be obtained for example as solid plugs, powders, or films by methods such as precipitation, crystallization, freeze drying, spray drying, or evaporative drying. They may be administered alone or in combination with one or more other compounds of the invention or in combination with one or more other drugs. Generally, they will be administered as a formulation in association with one or more pharmaceutically acceptable excipients. The term "excipient" is used herein to describe any ingredient other than the compound(s) of the invention. The choice of excipient depends largely on factors such as the particular mode of administration, the effect of the excipient on solubility and stability, and the nature of the dosage form.

The compounds of the present invention or any up thereof may be ated into various pharmaceutical forms for administration purposes. As appropriate compositions there may be cited all compositions usually employed for ically administering drugs. To prepare the pharmaceutical compositions of this invention, an effective amount of the ular compound, optionally in addition salt form, as the active ingredient is ed in te admixture with a pharmaceutically acceptable carrier, which carrier may take a wide variety of forms depending on the form of preparation desired for administration. These pharmaceutical compositions are desirably in unitary dosage form suitable, for example, for oral, , or percutaneous administration. For example, in preparing the compositions in oral dosage form, any of the usual pharmaceutical media may be employed such as, for example, water, glycols, oils, alcohols and the like in the case of oral liquid ations such as suspensions, syrups, elixirs, ons, and solutions; or solid carriers such as starches, sugars, kaolin, diluents, lubricants, binders, disintegrating agents and the like in the case of powders, pills, capsules, and tablets.

Because of their ease in administration, tablets and capsules represent the most advantageous oral dosage unit forms, in which case solid pharmaceutical rs are obviously employed. Also included are solid form preparations that can be converted, shortly before use, to liquid forms. In the compositions suitable for percutaneous administration, the carrier optionally comprises a ation enhancing agent and/or a le wetting agent, optionally combined with suitable additives of any nature in minor proportions, which additives do not introduce a significant deleterious effect on the skin. Said additives may facilitate the administration to the skin and/or may be helpful for preparing the desired itions. These itions may be stered in various ways, e.g., as a transdermal patch, as a spot-on, as an ointment.

The compounds of the present invention may also be administered via inhalation or insufflation by means of methods and formulations ed in the art for administration via this way. Thus, in general the compounds of the present invention may be administered to the lungs in the form of a solution, a suspension or a dry .

It is especially advantageous to formulate the aforementioned pharmaceutical compositions in unit dosage form for ease of stration and uniformity of dosage. Unit dosage form as used herein refers to physically discrete units suitable as unitary dosages, each unit containing a predetermined quantity of active ingredient calculated to produce the d therapeutic effect in ation with the required pharmaceutical carrier. Examples of such unit dosage forms are tablets (including scored or coated tablets), capsules, pills, powder packets, wafers, suppositories, injectable solutions or suspensions and the like, and segregated multiples thereof.

Those of skill in the treatment of infectious diseases will be able to determine the effective amount from the test results presented hereinafter. In l it is contemplated that an effective daily amount would be from 0.01 mg/kg to 50 mg/kg body weight, more preferably from 0.1 mg/kg to 10 mg/kg body . It may be appropriate to administer the required dose as two, three, four or more sub-doses at appropriate intervals hout the day. Said sub-doses may be formulated as unit dosage forms, for example, containing 1 to 1000 mg, and in ular 5 to 200 mg of active ingredient per unit dosage form.

The exact dosage and frequency of administration depends on the particular compound of formula (I) used, the particular condition being treated, the severity of the condition being treated, the age, weight and general physical condition of the particular t as well as other medication the individual may be taking, as is well known to those skilled in the art. Furthermore, it is evident that the effective amount may be lowered or increased depending on the response of the treated subject and/or depending on the evaluation of the physician prescribing the compounds of the instant invention. The effective amount ranges mentioned above are therefore only guidelines and are not intended to limit the scope or use of the invention to any extent.

Pre aration of com ounds offormula | Overall scheme. Compound A was ed according to procedures described in W02008147697 and W02009067081. 2014/053273 MsCI, Et3N 3N3 /\(S) ‘ \ /\(S€| HO/\\" \ NH DCM,OOC MSO NH 3 DMF, 70 0C NH BOC Boc BOC A B c dioxane/HCI HN N NH2 —> \ /\ S ‘ NH HCI —> ’ CH2C|2, rt 2 (S L K2C03 ,EtOH MW, 120 0C, 0.5 h S E Oxone H20, DMF | | O \ N Na|O4 O I A N water, EtOH, rt | A HI?! N NH2 Hg N NH2 (3) (S) 40 "O ? I \ Experimental Section MsCI, Et3N (8) (3) HO/\\v. /\ "- \ NH MSO DCM, 0 0C [NH BOC 300 A B Triethylamine (10.5 9, 103.75 mmol, 2.4 eq.) was added to the solution of A (10 g, 43.23 mmol, 1 eq.) in CH2C|2 (200 mL) at 0°C. Methanesulfonyl chloride (6.4 g, 55.87 mmol, 1.3 eq.) was added se to the solution and stirred 1.5 hours at 0°C. CHZCI2 (500 mL) was added. The solution was washed with aq. NaH003, brine, and dried over Na2804, the solids were removed by filtration and the solvent of the filtrate was removed under reduced pressure to give B. Used as such without further purification.

/\(S) —>. \ /\(3) Boo Boo B C A mixture of B (12 g, 38.782 mmol, 1 eq.) and sodium thiomethoxide (4.08 g, 58.17 mmol, 1.5 eq.) in DMF (60 mL) was stirred overnight at 70°C. The solids were removed by filtration and the ts of the filtrate were removed under d pressure. The crude was dissolved in ethyl acetate, washed with water, brine, dried over Na2804‘ the solids were removed by filtration and the solvents of the filtrate were removed under reduced pressure. The crude was purified by silica gel column tography (eluent: petroleum ether / ethyl acetate from 40/1 to 3/1) to afford C. 1H NMR (400 MHz, chloroform-d) 8 ppm 0.70 — 0.85 (m, 5 H), 1.15 — 1.49 (m, 13 H), 1.49 — 1.61 (m, 1 H), 1.61 — 1.80 (m, 1 H), 2.05 (s, 3 H), 2.38 - 2.50 (m, 2 H), 3.51 (br. s.,1 H), 4.25 (br. s., 1 H) dioxane/HCI ‘3) —> ‘8) . \ ". l}lH CH20I2, rt s/\‘ NH2'HCI c D HCI/dioxane (47 mL, 187.43 mmol, 10 eq.) was added drop wise to a stirred solution of C (4.9 g, 18.74 mmol, 1 eq.) in CH2CI2 at 0°C, and stirred for 1 hour at 25°C. The solution was concentrated under reduced pressure to give D.

Used as such in the next step.

O o \N \ l A 3QN CI N NH2 HN N NH2 \S/\\"‘ NH2_HC| .,l K2C03 ,EtOH MW, 120 0c, 0.5 h ’L WO 28189 D (0.75 g, 3.79 mmol, 1 eq.), 2-aminochloromethoxypyrimidine (0.908 g, .69 mmol, 1.5 eq.) and K2C03 (1.57 g 11.38 mmol, 3 eq.) were mixed in ethanol (20 mL). The mixture was stirred at 120°C in the microwave for 30 minutes. The solvent was removed under reduced pressure. The crude was purified by preparative silica thin layer chromatography (eluent: CH2C|2: CH3OH = 20:1) to afford E. 1H NMR (400 MHz, chloroform—d) 6 ppm 1.05 — 1.15 (m, 3 H), 1.40 - 1.60 (m, 4 H), 1.95 (m, 2H), 2.15 (m, 1 H), 2.30 (d, 3 H), 2.70 (t, 1 H), 2.90 (t, 1 H), 3.55 (m, 1 H), 4.50 (m, 1 H), 3.95 (s, 3 H), 6.20 (d, 1H), 6.60 (br. s., 2 H), 7.45 (s, 1 H) O O A Oxone Hl§| NANH 2 2 ., H20, DMF L (3) Oxone (6.959 g, 11.32 mmol, 3 eq.) was added to a solution of E (1.45 g, 3.773 mmol, 1 eq.) in DMF (100 mL) and water (100 mL). The mixture was stirred for 12 hours at 20°C. The solids were removed by filtration and the te was basified to pH=8 with saturated, aq. Na2C03 on. The resultant mixture was concentrated under reduced pressure. The residue was purified by preparative high-performance liquid chromatography (column: gemini 150 x mm x 50m, C18, mobile phase: CH3CN/water (0.05% HCI), Gradient: 2-32% CchN, 0-8min, flow rate: 30mL /min). The best fractions were pooled and concentrated under d pressure to afford 1.

LC-MS 3.88 min 1H NMR (400 MHz, methanol-d4) 8 ppm 0.92 (t, J=6.9 Hz, 3 H), 1.21 - 1.50 (m, 4 H), 1.69 (q, J=7.1 Hz, 2 H), 1.95 - 2.28 (m, 2 H), 2.98 (s, 3 H), 3.09 - 3.22 (m, 2 H), 3.87 (s, 3 H), 4.37 - 4.55 (m, 1 H), 7.26 (s, 1 H) labile protons not observed.

(I) | m o / m/ HN N NH2 Nam—,4 HN N NH2 (3)., (s ’I Hzo-EtOH, rt "I, A on of E (40 mg, 0.14 mmol, 1 eq.) in ethanol (40 mL) was treated with a solution of NalO4 (0.2 g, 1 mmol, 7.5 eq.) in water (10 mL), and then stirred at room temperature overnight. The solution was concentrated under vacuum.

The residue was d with water and extracted with ethyl acetate. The combined c layers were washed with brine, dried over NaZSO4, the solids were removed via filtration, and the solvent of the filtrate was removed under reduced pressure. The crude was purified by preparative high-performance liquid chromatography (C18 column, eluent: CH3CN, H20 from 3/97 to 33/67, 0.05% HCI). The desired fractions were collected and concentrated under vacuum to afford 2.

LC-MS 3.78 min 1H NMR (400 MHz, ol-d4) 8 ppm 0.90 (t, J=6.8 Hz, 3 H), 1.19 - 1.49 (m, 4 H), 1.67 (d, J=6.5 Hz, 2 H), 1.91 - 2.15 (m, 2 H), 2.63 (br. s., 3 H), 2.69 - 2.96 (m, 2 H), 3.85 (s, 3 H), 4.46 (br. s., 1 H), 7.25 (s, 1 H) labile protons not observed.

LC-MS Analytical .

Column YMC-PACK ODS—AQ, 50X2.0mm, A:H20 (0.1%TFA) B:acetonitrile (0.05%TFA) TIME(min) A% 8% 0 100 0 Mobile Phase 1 100 0 40 60 7.5 40 60 8 100 0 Flow Rate 0.8mL/min Wavelenoth UV 220nm Column 50°C ture MS oolarit oositive LCMS Agilent 1100 Biolo icalActivit ofcom ounds offormula | Description of Biological Assays Assessment of TLR7 and TLR8 activity The ability of compounds to activate human TLR7 and/or TLR8 was assessed in a cellular reporter assay using HEK293 cells transiently transfected with a TLR7 or TLR8 expression vector and NFKB-IUC reporter uct. y, HEK293 cells were grown in culture medium (DMEM supplemented with 10% FCS and 2 mM Glutamine). For transfection of cells in 15 cm dishes, cells were detached with Trypsin-EDTA, transfected with a mix of CMV-TLR7 or TLR8 plasmid (1700 ng), NFKB-IUC d (850 ng) and a transfection reagent and incubated for 48 h at 37°C in a humidified 5% C02 atmosphere.

Transfected cells were then washed in PBS, detached with Trypsin-EDTA and resuspended in medium to a density of 1.25 x 105 cells/mL. Forty microliters of cells were then dispensed into each well in 384-well plates, where 200 nL of compound in 100% DMSO was already present. ing 6 hours incubation at 37°C, 5% 002, the luciferase activity was determined by adding 15 uL of Steady Lite Plus substrate n Elmer) to each well and readout performed on a ViewLux ultraHTS microplate imager (Perkin Elmer). Dose response curves were ted from measurements performed in quadruplicates.

Lowest effective concentrations (LEC) values, d as the concentration that induces an effect which is at least two fold above the standard ion of the assay, were determined for each compound.

Compound toxicity was determined in parallel using a similar dilution series of compound with 40 uL per well of cells transfected with the CMV—TLR7 construct alone (1.25 x 105 cells/mL), in 384-well plates. Cell viability was measured after 6 hours incubation at 37°C, 5% C02 by adding 15 uL of ATP lite (Perkin Elmer) per well and reading on a ViewLux ultraHTS microplate imager n Elmer). Data was ed as CC50.

In parallel, a similar dilution series of compound was used (200 nL of compound in 100% DMSO) with 40 uL per well of cells transfected with NFKB- Iuc reporter construct alone (1.25 x 105 cells/mL). Six hours after incubation at 37°C, 5% C02, the Iuciferase ty was ined by adding 15 ul of Steady Lite Plus substrate (Perkin Elmer) to each well and readout performed on a ViewLux ultraHTS microplate imager (Perkin Elmer). Counterscreen data is reported as LEC. tion of ISRE promoter elements The potential of compounds to induce IFN-l was also evaluated by ing the activation of interferon—stimulated responsive elements (ISRE) by conditioned media from PBMC. The ISRE t of sequence GAAACTGAAACT is highly responsive to the STAT1-STAT2-IRF9 transcription factor, activated upon binding of lFN-l to their receptor IFNAR (Clontech, PT3372-5W). The plasmid plSRE-Luc from Clontech (ref. 631913) contains 5 copies of this ISRE element, followed by the firefly Iuciferase ORF. A HEK293 cell line stably transfected with plSRE-Luc (HEK-lSREluc) was established to profile the ioned PBMC cell culture media.

Briefly, PBMCs were prepared from buffy coats of at least two donors using a standard Ficoll centrifugation ol. Isolated PBMCs were resuspended in RPMI medium supplemented with 10% human AB serum and 2 x 105 cells/well were dispensed into 384-well plates containing compounds (70 uL total -1 3- volume). After overnight incubation, 10 uL of supernatant was transferred to ll plates containing 5 x 103 HEK-lSREluc cells/well in 30 uL (plated the day before). Following 24 hours of incubation, activation of the ISRE elements was measured by assaying luciferase ty using 40 uL/well Steady Lite Plus substrate (Perkin Elmer) and measured with ViewLux TS microplate imager (Perkin Elmer). The stimulating ty of each compound on the HEK- lSREluc cells was reported as LEC value, defined as the nd concentration applied to the PBMCs resulting in a luciferase activity at least two fold above the standard deviation of the assay. The LEC in turn indicates the degree of ISRE activation on transfer of a defined amount of PBMC culture medium. Recombinant interferon d-2a (Roferon-A) was used as a standard control compound.

TABLE I: ICAL ACTIVITY.

Human TLR 7 Human TLR 8 HEK-ISRE luc (LEC) uM (LEC) uM (LEC) uM NA = not available. All compounds showed no toxicity up to the highest tested concentration. All compounds showed no activity (LEC >25 (M) in the HEK 293 NF—kB counterscreen assay described above.

Claims (9)

Claims 1.

1. A method of making a compound of formula (I) or a pharmaceutically acceptable salt thereof, n X represents S, S=O or O=S=O, R1 is hydrogen, straight-chain or ed-chain -alkyl, (C1-6)-alkoxy or aryl, R2 is straight-chain or branched-chain (C1-3)-alkyl or (C3-6)-cycloalkyl and n = 1 or 2; the method comprising: (1) reacting a nd of formula A-1: (A-1), or a hydrochloride salt thereof, with a base and a compound of formula B-1: (B-1) to form a compound of formula (I) wherein X represents S; the method optionally further comprising: (2-a) reacting the compound of formula (I) wherein X represents S with sodium periodate to form a compound of formula (I) wherein X represents S=O; or (2-b) reacting the compound of formula (I) wherein X represents S with oxone to form a compound of formula (I) n X represents O=S=O.

2. The method of claim 1, wherein the base in step (1) is potassium carbonate.

3. The method of claim 1, wherein step (1) is performed under microwave conditions.

4. The method of claim 1, wherein step (2-a) is performed in a solvent comprising one or more polar protic solvents.

5. The method of claim 1, n step (2-b) is performed in a solvent comprising water.

6. The method of claim 1, wherein the product of step (I) has the following structure:

7. The method of claim 1, wherein the product of step (2-a) has the following structure:

8. The method of claim 1, wherein the product of step (2-b) has the following structure: HN N NH2 O .

9. The method of claim 1, substantially as herein bed with reference to the Experimental Section.