PROCESS FOR THE PREPARATION OF 2-HALOMETHYL-PENEMS AND THEIR USE FOR THE PREPARATION OF ANTIBACTERIAL PENEMS

Abstract: It is described a process for the preparation of 2-halomethyl-penems (in particular 2-chloromethyl-penems) comprising, as intermediate step, the formation of the corresponding 2-haloacetylthio-azetidone.

Description: Process for the preparation of 2-halomethyl-penems and their use for the preparation of antibacterial penems. Field of the invention The present invention refers to a process for the preparation of 2- halomethyl-penems {in particular 2-chloromethyl-penems) useful for the preparation of antibacterial penems. State of the art It is known that penem-derivatives are compounds endowed with a wide activity spectrum against bacteria [see for example Wise R. "The Carbapenem and Penem Antibiotics - A Brief Review" - Antimicrob. Newsl. 7. 73 - 80 (1990)]. It is also known that 2-halomethyl-penems of formula (I) (in particular 2-chloromethy1-penems) are useful intermediates for the preparation of antibacterial penems [G. Pentassuglia et al. J of Antibiotics Vol. 48, 399 - 07 (1995)]- The processes for the preparation 2-halomethyl-penems (I) known up to now [see for example Altamura M. et al. J. Org. Chem. 1993, 58, 272-274] comprise a step involving the corresponding 2-hydroxymethyl-penem (II): wherein R^ and R are as hereinafter defined. The preparation of compound (II) requires a long serie of complicated steps, giving low yields and involving the use of protecting groups and expensive reagents, which are not suitable for industrial production. Moreover, the synthesis of (II) requires many chromatographic separations for the purification of the obtained compounds since their use as crude products in the following acid or basic reaction conditions is not suitable because of their low stability. Summary of the invention The present invention refers to a process for the preparation of 2- halomethyl-penems (in particular 2-chloromethyl-penems) of formula (I) wherein R-^ is a protecting group for the alcoholic hydroxyle, R is a protecting group for the carboxyle and X is an halogen, in particular chorine, comprising, as intermediate step, the formation of the corresponding 2-haloacetylthio-azetidone. Detailed descritpion of the invention It was now found, and it is an object of the present invention, a process which permits to obtain the 2-halomethyl-penems (I) (in particular 2-chloromethyl-penems) with only three steps using as starting product a product which is easily commercialy available. The synthesis path, described in the enclosed Schema, permits to obtain the compounds of formula (I) without requiring intermediate steps involving protection and deprotection and using, for the construction of the final product, all the carbon atoms added during the synthesis. Moreover the process object of the present invention does not involve the complicated methods of separation or purification of the intermediates and therefore it allows to obtain the compounds of formula (I) with high yields. Moreover the reaction conditions allow to obtain the compounds (I) with high stereoselectivity since during the process according to the invention only the wanted optical isomer is formed. The 2-halomethyl-penems of formula (I) can be directly transformed, after removing the protective groups, into the wanted final products. As reported in the Schema the process according to the invention comprises the reaction between a compound of formula (III), (3R.4R)-4- acetoxy-3-[R^0-ethyl]-2-azetιdιnone, wherein R-^ is as defined above, and a 2-halothιoacetιc acid (IV) wherein X is an halogen, prepared, for example, as described in: Arndt, Bekir Beπchte, 63B, 2390 (1930). The reaction is carried out in an organic non-protic solvent, preferably dioxane, tetrahydrof urane , chloroform at a temperature of -10°C - +4θ°C, in the presence of an organic base, as tπethylamme or dusopropylethylamine , and of a Lewis acid, as zinc iodide, zinc bromide, zinc chloride, aluminium chloride. The 2-haloacetylthιo azetidone (V) can be reacted, without further purification, with an oxallyl chloride ester (VI) . Such reaction is performed in a non-protic organic solvent, preferably dioxane, tetrahydrof urane , toluene, chloroform, at a temperature of -60°C - +20°C. preferably -20°C - +10°C, in the presence of an organic base, as triethylamme or dusopropylethylamine. The intermediate (VII), acylated on the β-lactamic nitrogen, is cyclized into the corresponding 2-halomethyl-penem (I), under the action of an organic phosphite, as triethylphosphite or trimethyl -phosphite, or phosphonite, as dimethoxymethylphosphine, in an organic solvent as toluene, xylene, chloroform, methylene chloride, at a temperature of 20°C - l4θ°C, for a time of 1 - 120 h. The reaction mixture containing the crude 2-halomethyl-penem (I) can be used directly, without further purification, to obtain the wanted penem-derivatives (for example as described in US-4,794,109) • In particular the present invention refers to a process for the preparation of 2-chloromethyl-penems [compounds of formula (I) wherein X = CI, R^ and R are as above defined]. According to the invention the group Ri , protecting the alcoholic hydroxy1-group is preferably a tri-C^_galchyl-silyl (in particular terr-butyl-dimethyl-silyl and trimethylsilyl), allyloxycarbonyl, p- nitrobenzyloxycarbonyl; while the group R , protecting the carboxyl- group, is preferably allyl, benzyl (possibly substituted with a methoxy- or nitro-group) , CH2θCO(0) m R j wherein R^ is a C 1 _galkyl-group and a is 0 or 1. Halogen according to the present invention is: chlorine, bromine, iodine, in particular chlorine. The following examples are reported to better illustrate the invention. EXAMPLE 1 (3S,4R)-3-r(R)-rert-butyldimethylsilyloxy)ethyl1-4-(2-chloro- acetylthio)-2-azetidone 83-3 g (0.261 moles) of zinc iodide are added, at 20°C under nitrogen, in a solution of 50 g (0.174 moles) of (3R.4R)-4-acetoxy- 3 -[(R)- tertbutyldimethylsilyloxy)ethyl] - 2 -azetidone; after 1 minutes 38-3 g (0.346 moles) of 2-chloroacetic acid are added. The mixture is cooled down to 12°C and thereafter, in 1 h, a solution of 26.5 ml (0.190 moles) of triethylamine in dioxane (50 ml) is added therein. The mixture is stirred for 2 h at the same temperature. 5-0 ml (O.O36 moles) of triethylamine are added and the mixture stirred for 30 minutes. The solution is poured in a cold solution of NaHSOn 3% and extracted with ethylacetate. The organic phase is washed with solutions of NaHSO 3% , NaHCO 5% . water, NaCl 10% and dried on anhydrous Na 2 S0 / ,. By evaporating the solvent, under vacuum, a yellow-brownish is obtained. Ethylether is added, the solvent is evaporated and a pale- yellow solid is obtained. Yield: 57 g (97%) - IH NMR (200 MHz) (CDC1 3 ) : d 0.07 (3H, s) , 0.08 (3H, s) , 0.88 (9H, s) , 1.21 (3H, d, J = 6.3 Hz), 3-23 (IH. dd, J = 2.3, 4.0 Hz), 4.22 (2H, s), 4.27 (IH, qd. J = 3-7, 6.3 Hz), 5-32 (IH, d, J = 2.3 Hz), 6.4 (IH, br s). 13 C NMR (50 MHz) (CDC1 3 ) : d -4.3, ~5-l. 17-9. 22.3, 2 .7, 48.0, 52.4, 64.6, 65.4, 166.1. 194.8. MS TS (m/z): (M+H) + 338, (M+NH 4 ) + 3 - EXAMPLE 2 (3S,4R)-l-(allyloxyoxalyl)-3-r(R)-tert-butyldimethyl-silyloxy)-ethyl]- 4-(2-chloroacetylthio)-2-azetidone To a solution of 57 g (O.I69 moles) of (3S,4R)~3~[ (R) - tevt- butyldimethylsilyloxy)ethyl]-4-(2-chloro-acetylthio)-2-azetidone in anhydorus tetrahydrofurane (500 ml) 42.3 ml (0.338 moles) of allyloxyoxalyl chloride are added, at 0°- 3°C, under nitrogen. The mixture is stirred for some minutes and then a solution of 43-4 ml (0.25 moles) of dusopropylethylamine in tetrahydrofurane (40 ml) is added, drop by drop, in minutes. The mixture is stirred 30 minutes at the same temperature. 15 ml (0.087 moles) of dusopropylethylamine are added, the solution stirred 30 minutes and filtered. 5 The filtrate is poured in a cold solution of NaHCO % and extracted with n-esane, washing with the same solvent the solid remained on the filter. The organic phases are pooled together, washed with water and NaCl 10% and dried on anhydrous Na ? S0 /j . By evaporating the solvent a brownish oil is obtained which is used in the following step without ° further purification. Yeld: 73.0 g (96%). 1 H NMR (200 MHz) (CDClj) : d -0.04 (3H, s) , -0.09 (3H, s) , O.85 (9H, s), 1.24 (3H, d, J = 6.3 Hz), 3.5 (IH, t, J = 3 Hz), 4.26 (2H. s). 4.38 (IH, qd, J = 3, 6.3 Hz). 4.70-4.82 (2H, m) , 5-22-5.46 (2H, m) , 5 5.80-6.06 (IH, m), 5.97 (IH, d, J = 3 Hz). 13 C NMR (50 MHz) (CDC1 3 ) : d -5.2, -4.3, 17.8, 21.7. 25.6, 47.9, 53-8, 64.7, 66.3, 67.4, 120.1. 130.5, 154.5, 159-0, 162.9, 190.7- MS TS (m/z): (M+NH 4 ) + 467. EXAMPLE 3 Allyl (5R,6S)-2-chloromethyl-6-( (R)-l-tert-butyldimethylsilyloxy- 0 ethyl)-penem-3-carboxylate■ To a solution of 73 g (0.162 moles) of (3S,4R)-l-(allyloxyoxalyl)-3- [ (R)-rert-butyldimethyl-silyloxy)-ethyl]-4-(2-chloroacetylthio)-2- azetidone in 730 ml toluene 59 g (0.356 moles) of triethylphosphite are added. The solution is refluxed for 3 h. The solution is cooled 5 a nd concentrated under vacuum giving, after column chromatography (silica gel; cyclohexane/ethylacetate :1 v/v), the wanted allyl (5R.6S)-2-chloromethyl-6-( (R)-l-tert-butyldimethylsilyloxy-ethyl)- penem-3-carboxylate as a yellow oil. Yeld 82%. HPLC: 1) Column: Hypersil 5 ODS 5mm C- ^ g, 4.6 x 250 mm; mobile phase: water/acetonitrile 20:80 v/v; flux = lml/min, 1 = 220, 320 nm; t^ = 8.4 min. 2) Column: BondClone 10, 10 mm, C-^g, 3-9 x 300 mm, mobile phase: water/acetonitrile 20:80 v/v, flux = lml/min, 1 = 205, 5 nm) ; tp = 9-6 min. 1 H NMR (200 MHz) (CDC1 3 ) : d 0.07 (6H, s) , O.87 (9H, s) , 1.23 (3H, d, J = 6.2 Hz), 3-73 (IH, dd, J = 1.6, 4.3 Hz), 4.60-4.81 (2H, m) , 4.62 and 4.94 (2H, ABq, J = 14 Hz), 5-20-5-47 (2H, m) , 5-63 (IH, d, J = 1.6 Hz), 5-81-6.03 (IH. m). 13 C NMR (50 MHz) (CDClj) : d -5-3. "4.7, 17-9, 22.3, 25-6, 37-6 (CH 2 -C1). 62.4, 64.9, 65.9. 72.0, 118.6, 121.8, 131.2, 150.9, 158.9, 172-3- MS El: (m/z) 417 (M+). EXAMPLE 4 To a solution of 19 g (O.O56 moles) of (3S.4R)-l-(allyloxyoxalyl)-3- [(R)- tert-butyldimethyl-silyloxy)-ethyl]-4-(2-chloroacetylthio)-2- azetidone in anhydrous toluene (150 ml) 14.1 ml (0.113 moles) of allyloxyoxalyl chloride are added under nitrogen at 0°- 3°C. The solution is stirred for some minutes and then a solution of 11.7 ml (0.084 moles) triethylamine in toluene (10 ml) is added drop by drop. The solution is stirred for 90 minutes at the same temperature. 3-9 ml (0.028 moles) triethylamine are added, the solution stirred 0 minutes and filtered. The filtrate is washed with a cold aqueous solution of NaHC0 3 5%, with water and with a solution of NaCl 10%; thereafter the solution is dried on anhydrous Na 2 S0^ and filtered. 20.4 g (0.123 moles) of triethyl-phosphite are added and the mixture is refluxed for 3 h. The solution is cooled, concentrated under vacuum and purified by column chromatography (silica gel; cyclohexane/ethyl acetate 3:1 v/v), giving the wanted allyl (5R,6S)-2-chloromethyl-6- ( (R) -1- tert- butyldimethylsilyloxy-ethyl)-penem-3-carboxylate as a yellow oil. Yield: 71%. (HI) (IV) (V) COC1 COOR 2 (VI) (I) (VII)

Claims: CLAIMS 1. Process for the preparation of 2-halomethyl-ρenems of formula (I' wherein R-, is a protecting group for the alcoholic hydroxyle , R 2 is a protecting group for the carboxyle and X is an halogen, comprising, as intermediate step , the formation of the corresponding 2- haloacetylthio-azetidone (V) (V) wherein X is halogen. 2. Process according to Claim 1 wherein: a) compounds of formula (III) wherein R^ is as above defined, are reacted with a 2-halothioacetic acid in an organic solvent in the presence of an organic base and a Lewis acid, at a temperature of -10°C - +4θ°C, to give compounds of 6 formula (V) as defined in Claim 1; 7 b) the above said compounds of formula (V) are reacted w th an oxallyl 8 chloride ester m an organic solvent in the presence of an organic 9 base at a temperature of -60° - +20°C, preferably -20°C - +10°C, to ° give the compounds of formula (VII) - η wherein R-, R 2 and X are as above defined; 12 c) the compounds of formula (VII) are finally cyclized in an 13 appropriate solvent at 20° - l4θ°C for 1 - 120 h, under the action of 4 an organic phosphite or phosphonite. 1 3- Process according to Claim 1, for the preparation of derivatives of 2 general formula (I) wherein the protecting group R^ is selected from the group consisting of: tert-butyl-dimethyl-silyl, trimethylsilyl, 4 allyloxycarbonyl , p-nitrobenzyloxy-carbonyl ; and the group R 2 is selected from the group consisting of: allyl, benzyl (possibly 6 substituted with a metoxy- or nitro-group) , CH 2 0C0(0) m R^ wherein R^ is 7 a C-^.galkyl-group and m is 0 or 1; the organic base is preferably 8 triethylamine or dusopropylethylamine, the Lewis acid is selected 9 from the group consisting of: zinc iodide, zinc bromide, zinc 10 chloride, aluminium chloride and the organic phosphite or phosphonite 11 is a trimethyl-, triethyl-phosphite or a dimethoxymethylphosphme. 4. 12 Process according to claims 1 and 2 wherein the 2-halothιoacetιc acid - Il ¬ is the 2-chlorothιoacetιc acid. 5- Process according to Claim 3 wherein the obtained compound (I) is a compound of formula (I) according to claim 1 wherein: R-^ = tert- butyldimethylsilyl, R 2 = allyl, X = CI. 6. Compound of formula (V) wherein R^ and X are as above defined. 7- Compound of formula (VII) wherein R-^, R 2 and X are as above defined. 8. Compounds according to Claims 5 and 6 wherein X = chlorine.

Inventors: ALTAMURA MARIA, PERROTTA ENZO, ALTAMURA, MARIA, PERROTTA, ENZO
Applicants: ALTAMURA MARIA, LUSO FARMACO INST, MENARINI FARMA IND, PERROTTA ENZO, A. MENARINI INDUSTRIE FARMACEUTICHE RIUNITE S.R.L., ALTAMURA, MARIA, ISTITUTO LUSO FARMACO D'ITALIA S.P.A., PERROTTA, ENZO
Application year: 1997
Main classification: C07D499
IPC codes: C07D205, C07D499