Methods of synthesizing 1-(acyloxy)-alkyl carbamate prodrugs

1. A method for synthesizing a compound of Formula (I) or a pharmaceutically acceptable salt thereof comprising:

reacting a compound of Formula (V) or a salt thereof with a primary or secondary amine-containing drug HNR 9 R 10 to provide a compound of Formula (Ia):

and, when R 11 is a leaving group in the compound of Formula (Ia), the method comprises reacting the compound of Formula (Ia) or a salt thereof with a carboxylic acid of formula R 1 —COOH in the presence of an organic base, or with a salt of a carboxylic acid of formula R 1 —COOH to provide the compound of Formula (I) or a salt thereof; wherein:

R 1 is chosen from C 1-6 alkyl, substituted C 1-6 alkyl, C 3-6 cycloalkyl, substituted C 3-6 cycloalkyl, phenyl, substituted phenyl, and C 7-9 phenylalkyl;

R 11 is chosen from a leaving group and —OC(O)—R 1 ;

one of R 2 and R 3 is hydrogen and the other of R 2 and R 3 is chosen from hydrogen, C 1-4 alkyl, substituted C 1-4 alkyl, C 1-4 alkoxycarbonyl, C 3-6 cycloalkyl, C 3-6 cycloalkoxycarbonyl, phenyl, substituted phenyl, and C 7-9 phenylalkyl; or R 2 and R 3 together with the carbon atom to which they are bonded form a ring chosen from a cyclobutyl, cyclopentyl, and cyclohexyl ring;

R 4 is chosen from C 1-4 alkyl, substituted C 1-4 alkyl, phenyl, substituted phenyl, C 5-6 cycloalkyl, and substituted C 5-6 cycloalkyl; wherein each of the one or more substituent groups is independently chosen from halogen, halo-C 1-3 alkyl, hydroxyl, and cyano;

each of R 5 , R 6 , R 7 , and R 8 is independently chosen from hydrogen, halogen, C 1-3 alkyl, and halo-C 1-3 alkyl; and

—NR 9 R 10 is a moiety of a primary or secondary amine-containing drug corresponding to the removal of one hydrogen atom from a single nitrogen atom of a parent primary or secondary amine-containing drug having the structure HNR 9 R 10 , wherein R 9 is chosen from hydrogen and a bond to R 10 ; and

wherein —NR 9 R 10 is selected from acebutalol, albuterol, alprenolol, atenolol, bunolol, bupropion, butopamine, butoxamine, carbuterol, cartelolol, colterol, deterenol, dexpropanolol, diacetolol, dobutamine, exaprolol, exprenolol, fenoterol, fenyripol, gabapentin, labotolol, levobunolol, metolol, metaproterenol, metoprolol, nadolol, pamatolol, penbutalol, pindolol, pirbuterol, practolol, prenalterol, primidolol, prizidilol, procaterol, propanolol, quinterenol, rimiterol, ritodrine, solotol, soterenol, sulfiniolol, sulfinterol, sulictidil, tazaolol, terbutaline, timolol, tiprenolol, tipridil, tolamolol, thiabendazole, albendazole, albutoin, alendronate, alinidine, alizapride, amiloride, aminorex, aprinocid, cambendazole, cimetidine, cisapride, clonidine, cyclobenzadole, delavirdine, efeqatrin, etintidine, fenbendazole, fenmetazole, flubendazole, fludorex, icadronate, lobendazole, mebendazole, metazoline, metoclopramide, methylphenidate, mexiletine, neridronate, nocodazole, oxfendazole, oxibendazole, oxmetidine, pamidronate, parbendazole, pramipexole, prazosin, preqabalin, procainamide, ranitidine, tetrahydrazoline, tiamenidine, tinazoline, tiotidine, tocainide, tolazoline, tramazoline, xylometazoline, dimethoxyphenethylamine, n-[3(R)-[2-piperidin-4-yl)ethyl]-2-piperidone-l-yl]acetyl-3(R)-methyl-β-alanine, adrenolone, aletamine, amidephrine, amphetamine, aspartame, bamethan, betahistine, carbidopa, clorprenaline, chlortermine, dopamine, L-dopa, ephrinephrine, etryptamine, fenfluramine, methyldopamine, norepinephrine, enviroxime, nifedipine, nimodipine, triamterene, pipedemic acid, 1-ethyl-6-fluoro-1,4-dihydro-4-oxo -7-(1-piperazinyl) -1,8- napthyridine-3-carboxylic acid and 1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo- 7-(piperazinyl)-3-quinolinecarboxylic acid, theprubicin, deoxysperqualin, seglitide, nebracetam, benanomicin B, eremomycin, thrazarine, tosufloxacin, baogongteng A, angiopeptin, boholmycin, ravidomycin, tageflar, orienticins, amphotericin B, tiamdipine, doxorubicin, lysobactin, mofegiline, octreotide, oxolide, amikacin, phospholine, nuvanil, cispentacin, chlorotetain, remacemide, ramoplanins, janthinomycins, mersacidin, droxidopa, helvecardin A, helvecardin B, rilmazafone, vigabatrin, amlodipine, (R)-(+)-amlodipine, mideplanin, milnacipran, pranedipine, olradipine, deoxymethylsperqualin, fudosteine, trovafloxacin, ceranapril, restricticin, idarubicin, arbekacin, qiracodazole, poststatin, pazufloxacin, D-cycloserine, ovothiol A, ceftizoxime, icatibant, p-iodorubidazone, aladapcin, dalargin, seproxetine, pradimicin E, pradimicin FA-2, tafenoquine, sampatrilat, ruboxyl, dactimicin, alatrofloxacin, galarubicin, metaraminol, exatecan, squalamine, paromomycin, leustroducsin A, leustroducsin B, leustroducsin C, lanicemine, azoxybacilin, tetrafibricin, pixantrone, ziconotide, garomefrine, spinorphin, doripenem, alestramustine, seraspenide, safingol, aminolevulinic acid, pelagiomicin C, styloquanidine, L-4-oxalysine, eglumegad, rhodopeptins, mycestericin E, midaxifylline, anisperimus, lagatide, ibutamoren, oritavancin, ecenofloxacin, metyrosine, methyldopa, baclofen, tranylcypromine, micronomicin, zorubicin, epirubicin, qilatide, epithalon, cystamine, pluraflavin A, pluraflavin B, pasireotide, caprazamycin, barusiban, spisulosine, 21-aminoepothilone B, capsavanil, olcegepant, sulphostin, lobophorin A, papuamide A, papuamide B, cystocin, deoxyneqamycin, galnon, pyloricidin B, brasilicardin A, neramexane, kaitocephalin, icofunqipen, aliskiren, capromorelin, histaprodifen, donitriptan, cambrescidins, tipifarnib, tabimorelin, belactosin A, belactosin C, circinamide, tarqinine, sulphazocine, nepicastat, oseltamivir, hydrostatin A, butabindide, netamiftide, memantine, fluvoxamine, deferoxamine, tranexamic acid, fortimicin A, cefaclor, lisinopril, ubestatin, cefminox, aspoxicillin, cefcanel, cefcanel daloxate, olamufloxacin, R-(+)-aminoindane, gemifloxacin, kahalalide F, palau′amine, examorelin, leustroducsin H, sabarubicin, amifostine, L-homothiocitrulline, L-thiocitrulline, impentamine, neboglamine, amselamine, cetefloxacin, cyclothialidine, fluvirucin B2, loracarbef, cefprozil, sperabillins, milacainide, avizafone, α-methyltryptophan, cytaramycin, lanomycin, decaplanin, eflornithine, L-histidinol, tuftsin, kanamycin, amthamine, sitafloxacin, leurubicin, amantadine, isodoxorubicin, qludopa, bactobolin, esafloxacin, tabilautide, lazabemide, enalkiren, amrubicin, daunorubicin, mureidomycins, pyridazomycin, cimaterol, (+)-isamoltan, N-desmethylmilameline, noberastine, fosopamine, adaprolol pradimicin B, amosulalol xamoterol, boholmycin, risotilide, indeloxazine, denopamine, parodilol, utibapril, nardeterol, biemnidin, sparfloxacin, sibanomicin, tianeptine, oberadilol, methoctramine, sezolamide, anabasine, zilpaterol, zabiciprilat, enkastins, ulifloxacin, (+)-sotalol, deoxynojirimycin, altromycin A, altromycin C, dorzolamide, fepradinol, delapril, ciprofloxacin, balofloxacin, mepindolol, berlafenone, ramipril, dopexamine, dilevalol,(−)-nebivolol, duramycin, enalapril, meluadrine, zelandopam, voglibose, sertraline, carvedilol, pafenolol, paroxetine, fluoxetine, phendioxan, salmeterol, solpecainol, repinotan, bambuterol, safinamide, tilisolol, 7-oxostaurosporine, caldaret, sertraline, cilazapril, benazepril, prisotinol, gatifloxacin, ovothiol B, adaprolol, tienoxolol, fluparoxan, alprenoxime, efeqatran, pradimicin, salbostatin, ersentilide, (S)-noremopamil, esperamicin A1, batoprazine, ersentilide, osutidine, quinapril, dihydrexidine, argiopine, pradimicin D, frovatriptan, hispidospermidin, silodosin, michellamine B, sibenadet, tetrindol, talibegron, topixantrone, nortopixantrone, tecalcet, buteranol, α-methylepinephrine, nornicotine, thiofedrine, lenapenem, imidapril, epibatidine, premafloxacin, socorromycin, trandolapril, tamsulosin, dirithromycin, inogatran, vicenistatin, immepyr, immepip, balanol, orbifloxacin, maropitant, dabelotine, lerisetron, ertapenem, nolomirole, moxifloxacin, vofopitant, halofuqinone, melaqatran, ximelaqatran, fasudil, isofaqomine, pseudoephedrine, propafenone, celiprolol, carteolol, penbutolol, labetalol, acebutolol, reproterol, rimoterol, amoxapine, maprotiline, viloxazine, protriptyline, nortriptyline, desipramine, oxprenolol, propranolol, ketamine, butofilolol, flecainide, tulobuterol, befunolol, immucillin-H, vestipitant, cinacalcet, lapatinib, desloratadine, ladostiqil, vildagliptin, tulathromycin B, becampanel, salbutamol, delucemine, solabegron, paroxetine, qaboxadol, telavancin, ralfinamide, tomoxetine, dalbavancin, elarofiban, ferulinolol, fenoldopam, sumanirole, sarizotan, brinzolamide, pradofloxacin, qarenoxacin, reboxetine, ezlopitant, palindore, nebivolol, dinapsoline, proxodolol, repinotan, demexiptiline, mitoxantrone, norfloxacin, dilevalol, nipradilol, esmolol, ibopamine, troxipide, arotinolol, formoterol, bopindolol, cloranolol, mefloquine, perindopril, mabuterol, bisoprolol, bevantolol, betaxolol, tertatolol, enoxacin, lotrafiban, moexipril, droxinavir, adroqolide, alniditan, tiqecycline, lubazodone, meropenem, temocapril, napsamycins, (−)-cicloprolol, ecteinascidins, alprafenone, landiolol, tirofiban, noberastine, rasaqiline, setazindol, picumeterol, arbutamine, mecamylamine, delfaprazine, imidapril, midafotel, manzamines, binospirone, duloxetine, and litoxetine.

2. The method of claim 1 , comprising oxidizing a compound of Formula (IV) or a salt thereof to provide the compound of Formula (V) or a salt thereof:

3. The method of claim 2 , comprising treating the compound of Formula (IV) or a salt thereof with an oxidant chosen from peracetic acid, potassium peroxymonosulfate, and hydrogen peroxide.

4. The method of claim 2 , comprising reacting a compound of Formula (II) or a salt thereof with a compound of Formula (III) or a salt thereof to provide the compound of Formula (IV) or a salt thereof:

wherein L is chosen from a leaving group and —OC(O)—R 1 .

5. The method of claim 1 , wherein, when R 11 is a leaving group in a compound of Formula (V) the method comprises:

reacting the compound of Formula (V) or a salt thereof with a carboxylic acid of formula R 1 —COOH in the presence of an organic base; or

reacting the compound of Formula (V) or a salt thereof with a salt of a carboxylic acid of formula R 1 —COOH to provide the compound of Formula (V) or a salt thereof wherein R 11 is —OC(O)—R 1 .

6. The method of claim 4 , wherein, when R 11 is a leaving group and L is not halogen in a compound of Formula (II), the method comprises:

reacting the compound of Formula (II) or a salt thereof with a carboxylic acid of formula R 1 —COOH in the presence of an organic base; or

reacting the compound of Formula (II) or a salt thereof with a salt of a carboxylic acid of formula R 1 —COON to provide the compound of Formula (II) or a salt thereof wherein R 11 is —OC(O)—R 1 .

7. The method of claim 2 , wherein, when R 11 is a leaving group in a compound of Formula (IV) the method comprises:

reacting the compound of Formula (IV) or a salt thereof with a carboxylic acid of formula R 1 —COON in the presence of an organic base; or

reacting the compound of Formula (IV) or a salt thereof with a salt of a carboxylic acid of formula R 1 —COOH to provide the compound of Formula (IV) or a salt thereof wherein R 11 is —OC(O)—R 1 .

8. The method of claim 1 , wherein the salt of a carboxylic acid of Formula R 1 —OOH is chosen from the silver carboxylate of R 1 —COOH and the copper (I) carboxylate of R 1 —COOH.

9. The method of claim 1 , wherein R 11 is a leaving group and is halogen.

10. The method of claim 1 , wherein R 4 is methyl.

11. The method of claim 1 , wherein each of R 5 , R 6 , R 7 , and R 8 is hydrogen.

12. The method of claim 1 , wherein the compound of Formula (I) is a compound of Formula (4):

or a pharmaceutically acceptable salt thereof, wherein:

R 1 is chosen from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl, 1,1-diethoxyethyl, phenyl, and cyclohexyl;

one of R 2 and R 3 is hydrogen, and the other of R 2 and R 3 is chosen from hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, phenyl, and cyclohexyl; and

HNR 9 R 10 is [1-(aminomethyl)cyclohexyl]acetic acid.

13. The method of claim 12 , wherein the compound of Formula (4) is 1-{[(α-isobutanoyloxyethoxy)carbonyl]aminomethyl}-cyclohexane acetic acid.

14. The method of claim 1 , wherein the compound of Formula (I) is a compound of Formula (1):

or a pharmaceutically acceptable salt thereof, wherein:

R 1 is chosen from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl, 1,1-diethoxyethyl, phenyl, and cyclohexyl;

one of R 2 and R 3 is hydrogen, and the other of R 2 and R 3 is chosen from hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, phenyl, and cyclohexyl; and

HNR 9 R 10 is (R)-4-amino-3-(4-chlorophenyl)butanoic acid.

15. The method of claim 14 , wherein the compound of Formula (1) is (3R) -4-{[(1S)-2-methyl-1-(2-methylpropanoyloxy)propoxy]carbonylamino}-3-(4-chlorophenyl) butanoic acid or a salt thereof.

16. The method of claim 1 , wherein the compound of Formula (I) is a compound of Formula (2):

or a pharmaceutically acceptable salt thereof, wherein:

R 1 is chosen from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl, 1,1-diethoxyethyl, phenyl, and cyclohexyl;

one of R 2 and R 3 is hydrogen, and the other of R 2 and R 3 is chosen from hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, phenyl, and cyclohexyl; and

HNR 9 R 10 is (S)-3-(aminomethyl)-5-methyl-hexanoic acid.

17. The method of claim 16 , wherein the compound of Formula (2) is 1-(R) -3-({[1-(2-methylpropanoyloxy)ethoxy]carbonylamino}methyl)(3S)-5-methylhexanoic acid or a salt thereof.

18. The method of claim 1 , wherein the compound of Formula (I) is a compound of Formula (3):

or a pharmaceutically acceptable salt thereof, wherein:

R 1 is chosen from C 1-4 alkyl, phenyl, o-tolyl, and cyclohexyl;

one of R 2 and R 3 is hydrogen, and the other of R 2 and R 3 is chosen from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl, 1,1-diethoxyethyl, phenyl, and cyclohexyl;

R 20 is chosen from hydrogen, C 1-4 alkyl, benzyl, 4-methoxybenzyl, diphenylmethyl, triphenylmethyl, tirmethylsilyl, triethylsilyl, triisopropylsilyl, tert-butyldimethylsilyl, and phenyldimethylsilyl; and

HNR 9 R 10 is trans-4-(aminomethyl)-cyclohexanecarboxylic acid.

19. The method of claim 18 , wherein the compound of Formula (3) is trans-4-({[(1R/S)-1-(2-methylpropanoyloxy)ethoxy]carbonylamino}methyl)-cyclohexanecarboxylic acid or a pharmaceutically acceptable salt thereof.

20. A compound of Formula (IV) or a salt thereof:

wherein:

R 11 is chosen from a leaving group and —OC(O)—R 1 wherein R 1 is chosen from C 1-6 alkyl, substituted C 1-6 alkyl, C 3-6 cycloalkyl, substituted C 3-6 cycloalkyl, phenyl, substituted phenyl, and C 7-9 phenylalkyl;

one of R 2 and R 3 is hydrogen, and the other of R 2 and R 3 is chosen from hydrogen, C 1-4 alkyl, substituted C 1-4 alkyl, C 1-4 alkoxycarbonyl, C 3-6 cycloalkyl, C 3-6 cycloalkoxycarbonyl, phenyl, substituted phenyl, and C 7-9 phenylalkyl; or R 2 and R 3 together with the carbon atom to which they are bonded form a ring chosen from a cyclobutyl, cyclopentyl, and cyclohexyl ring;

R 4 is chosen from C 1-4 alkyl, substituted C 1-4 alkyl, phenyl, substituted phenyl, C 5-6 cycloalkyl, and substituted C 5-6 cycloalkyl; wherein each of the one or more substituent groups is independently chosen from halogen, halo-C 1-3 alkyl, hydroxyl and cyano; and

each of R 5 , R 6 , R 7 and R 8 is independently chosen from hydrogen, halogen, C 1-3 alkyl, and halo-C 1-3 alkyl.

21. A compound of Formula (V) or a salt thereof:

wherein:

R 11 is chosen from a leaving group and —OC(O)—R 1 wherein R 1 is chosen from C 1-6 alkyl, substituted C 1-6 alkyl, C 3-6 cycloalkyl, substituted C 3-6 cycloalkyl, phenyl, substituted phenyl, and C 7-9 phenylalkyl;

one of R 2 and R 3 is hydrogen, and the other of R 2 and R 3 is chosen from hydrogen, C 1-4 alkyl, substituted C 1-4 alkyl, C 1-4 alkoxycarbonyl, C 3-6 cycloalkyl, C 3-6 cycloalkoxycarbonyl, phenyl, substituted phenyl, and C 7-9 phenylalkyl; or R 2 and R 3 together with the carbon atom to which they are bonded form a ring chosen from a cyclobutyl, cyclopentyl, and cyclohexyl ring;

R 4 is chosen from C 1-4 alkyl, substituted C 1-4 alkyl, phenyl, substituted phenyl, C 5-6 cycloalkyl, and substituted C 5-6 cycloalkyl; wherein each of the one or more substituent groups is independently chosen from halogen, halo-C 1-3 alkyl, hydroxyl, and cyano; and

each of R 5 , R 6 , R 7 and R 8 is independently chosen from hydrogen, halogen, C 1-3 alkyl, and halo-C 1-3 alkyl.

22. The method of claim 1 , wherein —NR 9 R 10 is selected from alendronate, amifostine, rac-baclofen, R-baclofen, carbidopa, clonidine, ciprofloxacin, cisapride, daunorubicin, doxorubicin, fenoldopam, fenoterol, gabapentin, gentamycin, kanamycin, levodopa, meropenem, metazoline, neomycin, pamidronate, pregabalin, tobramycin, tranexamic acid, trovafloxacin, and vigabatrin.

23. The method of claim 1 , wherein —NR 9 R 10 is selected from R-baclofen, gabapentin, pregabalin and tranexamic acid.