Methods of Preparing Substituted Tetracyclines with Transition Metal

(19) & (11) EP 1 666 454 B1 (12) EUROPEAN PATENT SPECIFICATION (45) Date of publication and mention (51) Int Cl.: of the grant of the patent: C07C 237/26 (2006.01) C07C 231/12 (2006.01) 07.09.2011 Bulletin 2011/36 A61K 31/65 (2006.01) A61P 31/04 (2006.01) (21) Application number: 06005085.3 (22) Date of filing: 13.09.2000 (54) Methods of preparing substituted tetracyclines with transition metal-based chemistries Verfahren zur Herstellung von substituierten Tetracyclinen mit Hilfe von auf Übergangsmetalle basierten Chemikalien Techniques de preparation de tetracyclines substituees avec des solutions chimiques a base de metal de transition (84) Designated Contracting States: (74) Representative: Nash, David Allan AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU Haseltine Lake LLP MC NL PT SE Redcliff Quay 120 Redcliff Street (30) Priority: 14.09.1999 US 154701 P Bristol 12.09.2000 US 232091 P BS1 6HU (GB) (43) Date of publication of application: (56) References cited: 07.06.2006 Bulletin 2006/23 • AHMAD N ET AL: "Polynuclear Complexes of Bivalent Metal Ions with Antibiotic Tetracycline" (62) Document number(s) of the earlier application(s) in JOURNAL OF THE CHEMICAL SOCIETY OF accordance with Art. 76 EPC: PAKISTAN, CHEMICAL SOCIETY OF PAKISTAN, 00961860.4 / 1 240 133 KARACHI, PK, vol. 12, no. 2, 1990, pages 168-173, XP000943839 ISSN: 0253-5106 (73) Proprietor: TRUSTEES OF TUFTS COLLEGE • KOZA D J: "SYNTHESIS OF 7-SUBSTITUTED Medford MA 02155 (US) TETRACYCLINE DERIVATIVES" ORGANIC LETTERS, ACS, WASHINGTON, DC, US, vol. 2, (72) Inventors: no. 6, March 2000 (2000-03), pages 815-817, • Nelson, Mark L. XP000943852 ISSN: 1523-7060 Wellesley, MA 02481 (US) • Rennie, Glen Remarks: South Weymouth, MA 02190 (US) Thefile contains technical information submitted after • Koza, Darrell the application was filed and not included in this Westerly, RI 02891 (US) specification Note: Within nine months of the publication of the mention of the grant of the European patent in the European Patent Bulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with the Implementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). EP 1 666 454 B1 Printed by Jouve, 75001 PARIS (FR) EP 1 666 454 B1 Description BACKGROUND OF THE INVENTION 5 [0001] The development of the tetracycline antibiotics was the direct result of a systematic screening of soil specimens collected from many parts.of the world for evidence of microorganisms capable of producing bacteriocidal and/or bac- teriostatic compositions. The first of these novel compounds was introduced in 1948 under the name chlortetracycline. Two years later oxytetracycline became available. The detailed elucidation of the chemical structure of these agents confirmed their similarity and furnished the analytical basis for the production of a third member of this group in 1952, 10 tetracycline. By 1957, a new family of tetracycline compositions characterized chemically by the absence of the position 6 ring-attached OH group present in the earlier compositions was prepared and became publicly available in 1967; and minocycline was in use by 1972. Individual tetracycline- type agents are structurally compared within Table I below, with reference made the following structural formula: 15 20 25 Table I Congener Substituent(s) At Carbon Position Nos. 30 Chlortetracycline -Cl (7) Oxytetracycline -OH,-H (5) Demeclocycline -OH,-H;-Cl (6;7) Methacycline -OH,-H;=CH2 (5;6) Doxycycline -OH,-H;-CH ,-H (5;6) 35 3 Minocycline -H,-H;-N(CH3)2 (6;7) [0002] More recent research efforts have focused on developing new tetracycline antibiotic compositions effective under varying therapeutic conditions and routes of administration; and for developing new tetracycline analogues which 40 might prove to be equal or more effective then the originally introduced tetracycline families beginning in 1948. Repre- sentative of such developments include U.S. Patent Nos. 3,957,980; 3,674,859; 2,980,584; 2,990,331; 3,062,717; 3,557,280; 4,018,889; 4,024,272; 4,126,680; 3,454,697; and 3,165,531. It will be understood that these issued patents are merely representative of the range of diversity of investigations seeking tetracycline and tetracycline analogue compositions which are pharmacologically active. 45 [0003] Historically, soon after their initial development and introduction, the tetracyclines, regardless of specific for- mulation or chemical structure, were found to be highly effective pharmacologically against rickettsiae; a number of gram-positive and gram-negative bacteria; and the agents responsible for lymphogranuloma venereum, inclusion con- junctivitis, and psittacosis. Hence, tetracyclines became known as "broad spectrum" antibiotics. With the subsequent establishment of their in vitro antimicrobial activity, effectiveness in experimental infections, and pharmacological prop- 50 erties, the tetracyclines as a class rapidly became widely used for therapeutic purposes. However, this widespread use of tetracyclines for both major and minor illnesses and diseases led directly to the emergence of resistance to these antibiotics even among highly susceptible bacterial species both commensal and pathogenic - as for example pneumo- cocci and Salmonella. The rise of tetracycline-resistant organisms has resulted in a general decline in use of tetracyclines and tetracycline analogue compositions as antibiotics of choice. 55 2 EP 1 666 454 B1 SUMMARY OF THE INVENTON [0004] The present invention is directed to a minocycline-based compound selected from a compound having the following minocycline core structure: 5 10 15 in which R is selected from methyl, ethyl or propyl and which is substituted or derivatized at the 9- position by a substituent selected from alkynyl, cycloalkyl, aryl, alkylcarbonyl, arylcarbonyl, aryloxycarbonyl, hydroxy, cyano, alkoxy, aryloxy, 20 carboxyl, carboxamido, carboxy ester, and carbocyclic or heterocyclic groups; and 9-[3’-(E)-butylpropenoate] minocycline. [0005] In an embodiment, R is methyl. [0006] In another embodiment, the compound is 9-phenyl minocycline. [0007] Also described are novel chemistries which allow for the production of substituted tetracycline compounds 25 including substituted tetracycline compounds which exhibit significant antibacterial activity. The methods disclosed herein utilize reactive tetracycline-based precursor compounds, reactive organic substituent precursors and transition metals or transition metal catalysts under conditions such that a tetracycline compound substituted with the desired organic substituent is formed. A substituted tetracycline compound may be prepared by combining a reactive tetracycline- based precursor compound such as an arene tetracycline diazonium salt, and a reactive organic substituent precursor, e.g., 30 alkenes, substituted alkenes, vinyl monomers, aromatics and heteroaromatics, in the presence of a transition metal catalyst, such as palladium chloride, under conditions such that a tetracycline compound substituted with the organic substituentis formed. A substituted tetracycline compound may be prepared by contacting a reactive tetracycline chemical complex comprising a reactive tetracycline- based precursor compound and a transition metal or transition metal catalyst forming a reactive chemical intermediate with a reactive organic substituent precursor under conditions such that a 35 tetracycline compound substituted with the organic substituent is formed. [0008] Described herein are reactive tetracycline chemical complexes comprising a reactive tetracycline-based precursor compound and a transition metal catalyst forming a chemical intermediate, which can advantageously be used in the methods described herein. [0009] Also described are substituted tetracycline analogs, wherein the substituent (denoted herein as "Z") at the 40 desired position, e.g., 7, 9, 13, is connected with a -C-C- linkage, and wherein the substituent comprises an aromatic or heteroaromatic moiety. The substituent may also comprise a -C=C- bond adjacent to the -C-C- linkage, e.g., 45 50 wherein R2 and R 3 are each independently hydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, aryl, alkylcarbonyl, arylcarbonyl, alkoxycarbonyl, aryloxycarbonyl, amino, hydroxy, cyano, alkoxy, aryloxy, carboxyl, alkoxycarbonyl, aryloxycarbonyl; or R2 and R3, taken together, form a substituted or unsubstituted carbocyclic or heterocyclic ring having 5 to 15 atoms in the ring. 55 [0010] The methods and chemical intermediates disclosed herein allow for novel substituted tetracycline-type compounds and therapeutic methods and pharmaceutical compositions that comprise such compounds. [0011] The method includes providing Z substituents, above, on the basic tetracycline ring structure through a process involving forming a reactive intermediate (comprising a tetracycline arenediazonium salt in a preferred embodiment) at 3 EP 1 666 454 B1 the desired position and adding a reactive compound, e.g., a π-bond containing compound in the presence of a transition metal catalyst to that position. The reactive intermediate may be formed in situ. In an advantageous embodiment such substituents are provided on the D ring of the basic tetracycline ring structure, e.g., positions 7 and/or 9. In another advantageous embodiment, such substitutions may be made at position 13. Such synthetic schemes are heretofore 5 new in this art and advantageously allow for direct substitution

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