Patent Abstract:
provided in the following specification are precursors or synthons that are useful for the synthesis of various arabinose based chemical and radiochemical derivatives of nitroimidazole - containing azomycin arabinosides , such as radioiodinated 1 -#- d -- iodoarabinofuranosyl )- 2 - nitroimidazole , and radiofluorinated 1 -#- d -- iodoarabinofuranosyl )- 2 - nitroimidazole . such compounds are useful in imaging , therapy , or radiotherapy . further , various syntheses of said precursors / synthons and the incorporation of said precursors / synthons into kits is provided . the precursors / synthons provided herein allow for an improved and facile manufacturing process for nitroimidazole - containing azomycin arabinosides .

Detailed Description:
the present invention relates to the development of novel chemical precursors / synthons , and their chemical and radiochemical derivatives and methods . for example , derivatization with a radionuclide is used to synthesize and manufacture radiopharmaceuticals for use as radiodiagnostic , radiotherapeutic , radiochemotherapeutic and chemotherapeutic agents . in one embodiment , the present application describes the synthesis and development of novel precursors / synthons for synthesizing isotopically ( radio ) labeled sugars - and sugar - coupled molecules , and their chemical modifications . the radiolabeled products can be obtained by using a fully automated procedure that , after optimization of reaction parameters for the targeted molecule , can be adapted for use in automated manufacturing units . in another aspect of the present invention , the compositions and methods are suited for use in a cartridge device or micro reactor device , comprising one or more microfluidic channels or tubes ( also referred to as microchannels or capillaries ) having at least one cross - sectional dimension ( e . g ., height , width , depth , diameter ) suited for micro volumes . the microchannels make it possible to manipulate small volumes of liquid on . in one embodiment , the application describes a general scheme represented as : l is a leaving group joined to the molecule directly or via an intermediate moiety ( linker ) that is connected to the moiety . the term “ leaving group ” as used herein , refers to groups that are readily displaced , for example , by a nucleophile . such leaving groups are well known . non - limiting examples of ‘ l ’ include a halogen , alkyl / arylsulfonyloxy , substituted alkyl / arylsulfonyloxy etc ., substituted organometallic leaving groups e . g ., stannyl , substituted mercury - based leaving groups but not limited to these , substituted silyl or any moiety replaceable by the halogen , radiohalogen , nucleophile or electrophile , joined to the molecule directly or via an intermediate moiety ( i . e ., linker ) that is connected to the moiety . the term “ linker ” as used herein , refers to a chain substituted or unsubstituted , comprising , for example , 1 to 10 atoms and may comprise , for example , 1 , 2 or 3 adjacent or non - adjacent atoms or groups . the linker may also comprise part of a saturated , unsaturated , aralkyl or aromatic ring that may be unsubstituted or further substituted . the terms “ substituted ” or “ substituent ” as used herein , refer to a compound , moiety , or functional group comprising one or more hydrogen atom of which is substituted by a group ( a substituent ) such as a — c 1 - 5 alkyl , c 2 - 5 alkenyl , halogen or halo ( chlorine , fluorine , bromine , iodine atom ), — cf 3 , nitro , amino (— nh 2 , — nhr , — nr 2 , etc . . . . ), silylated amino (— nh — si — r 2 , — n —[ sir 2 ] 2 , where r may be same or different ), oxo ( i . e ., forming — c (═ o )—), — oh , silylated — oh (— o — si — r 3 where r may be same or different ), carboxyl (— cooh ), silylated carboxyl (— coo — sir 2 , where r may be same or different ), — cooc 1 - 5 alkyl , — oc 1 - 5 alkyl , — conhc 1 - 5 alkyl , — nhcoc 1 - 5 alkyl , — osoc 1 - 5 alkyl , — so oc 1 - 5 alkyl , — soonhc 1 - 5 alkyl , — nhso 2 c 1 - 5 alkyl , aryl , heteroaryl and the like , each of which may be further substituted . the term “ alkyl , as used herein , refers to a hydrocarbon chain , typically ranging from about 1 to 20 atoms in length . such hydrocarbon chains may be branched or straight chain , substituted or unsubstituted . the term “ aryl ” as used herein , refers to one or more aromatic rings . aryl includes multiple aryl rings that may be fused , as in naphthyl or unfused , as in biphenyl . aryl rings may also be fused or unfused with one or more cyclic hydrocarbon , heteroaryl , or heterocyclic rings . the term “ aralkyl ” as used herein , refers to one or more alkyl substituted aromatic rings . alkyl chains may be further substituted or unsubstituted . aryl includes multiple aryl rings that may be fused , as in naphthyl or unfused , as in biphenyl . aryl rings may also be fused or unfused with one or more cyclic hydrocarbon , heteroaryl , or heterocyclic rings . the term “ heteroaryl ” as used herein , is an aryl group containing from one to four heteroatoms , preferably n , o , or s , or a combination thereof . heteroaryl rings may also be fused with one or more cyclic hydrocarbon , heterocyclic , aryl , or heteroaryl rings . the term “ alkenyl ” as used herein , refers to a monovalent , unbranched or branched hydrocarbon chain having one or more double bonds . the double bond of an alkenyl group can be unconjugated or conjugated to another unsaturated group . in one example , r is — oh , — nh 2 , — sh , — bh 2 , f or combinations thereof , on precursor molecule a . when a contains more than one r , one of the r &# 39 ; s can be substituted with or without a linker to a homo or heteroaromatic moiety . the anomeric bond may be a / p . all configurations of the sugar moiety are contemplated . p = a , but represent the corresponding product core that is formed after the precursor &# 39 ; s reaction with x . in some examples , r is alkyl , alkenyl , aryl , heteroaryl , halogen , halo , — cf 3 , nitro , amino , silylated amino , oxo , — oh , — oc (═ o ) c 1 - 5 alkyl , — oc (═ o ) c 1 - 5 aryl , — oc (═ o ) c 1 - 5 aralkyl , — och 2 c ( c ═ o ) c 1 - 5 alkyl , — och 2 c (═ o ) c 1 - 5 aryl , — och 2 c (═ o ) c 1 - 5 aralkyl , — och 2 oc 1 - 5 alkyl , — osir 3 , — och 2 oc 1 - 5 alkyl , carboxyl , silylated carboxyl , — cooc 1 - 5 alkyl , — oc 1 - 5 alkyl , — conhc 1 - 5 alkyl , — nhcoc 1 - 5 alkyl , — osoc 1 - 5 alkyl , — sooc 1 - 5 alkyl , — soonhc 1 - 5 alkyl , — nhso 2 c 1 - 5 alkyl , or — ch 2 —( ch 2 ) n — osir 3 , each of which may be further substituted and wherein n = 0 - 6 . in some examples , r is — oh , — nh 2 , — sh , — bh 2 , — f , or — o - acetyl , — o - pivaloyl , — o - allyl , — o - allyloxycarbonyl , — o - benzyl , — o - benzyl , — o - benzyloxycarbonyl , — o - benzyloxymethyl , — o - tert - butoxycarbonyl , — o - tert - butyl , — o - tert - butyldimethylsilyl , — o - tert - butyldiphenyl silyl , — o - tert - butylmethylsilyl , — o - chloroacetyl , — o - diethylisopropylsilyl , — o - 3 , 4 - dimethoxybenzyl , — o - levulinoyl , — o - methylacetyl , — o - 4 - methoxybenzyl , — o - 4 - methoxybenzyloxymethyl , — o - 2 - methoxymethyl , — o - 2 - methoxyethoxymethyl , — o - methylthiomethyl , — o - 4 - nitrobenzyloxycarbonyl , — o - tetrahydropyran - 2 - yl , — o - thexyldimethylsilyl , — o - 2 , 2 , 2 - trichloroethoxycarbonyl , — o - triethylsilyl , — o - triisopropylsilyl , — o - trimethylsilyl , — o - 2 -( trimethylsilyl ) ethoxycarbonyl , — o - 3 -( trimethylsilyl ) ethoxymethyl , — o - triphenylsilyl , or — o - trityl . in some examples said leaving group l is halogen , alkylsulfonyloxy , perfluoroalkylsulfonyloxy , arylsulfonyloxy , substituted alkylsulfonyloxy , substituted arylsulfonyloxy , a substituted organometallic leaving group , a substituted mercury - based leaving group , substituted silyl , any moiety replaceable by halogen , radiohalogen , nucleophile or electrophile . in some examples leaving group is joined to said a directly or via an intermediate moiety that is connected to a . wherein the chiral centers may be ( r ) or ( s ) configuration ; l is halogen , alkylsulfonyloxy , perfluoroalkylsulfonyloxy , arylsulfonyloxy , substituted alkylsulfonyloxy , or substituted arylsulfonyloxy ; and r is h or — c (═ o ) r 1 , wherein r 1 is alkyl , aryl , aralkyl , heteroaryl , heterocyclic — ch 2 c ( c ═ o ) c 1 - 5 alkyl , — ch 2 c (═ o ) c 1 - 5 aryl , — ch 2 c (═ o ) c 1 - 5 aralkyl , — ch 2 oc 1 - 5 alkyl , — sir 3 , — ch 2 oc 1 - 5 alkyl , — ch 2 —( ch 2 ) n — sir 3 , or — ch 2 —( ch 2 ) n — osir 3 and n is 0 - 6 . in one example , r is h , - acetyl , - pivaloyl , - allyl , - allyloxycarbonyl , - benzyl , - benzyl , - benzyloxycarbonyl , - benzyloxymethyl , - tert - butoxycarbonyl , - tert - butyl , - tert - butyldimethylsilyl , - tert - butyldiphenylsilyl , - tert - butylmethylsilyl , - chloroacetyl , - diethylisopropylsilyl , - 3 , 4 - dimethoxybenzyl , - levulinoyl , - methylacetyl , - 4 - methoxybenzyl , - 4 - methoxybenzyloxymethyl , - 2 - methoxymethyl , - 2 - methoxyethoxymethyl , - methylthiomethyl , - 4 - nitrobenzyloxycarbonyl , - tetrahydropyran - 2 - yl , - thexyldimethylsilyl , - 2 , 2 , 2 - trichloroethoxycarbonyl , - triethylsilyl , - triisopropylsilyl , - trimethylsilyl , - 2 -( trimethylsilyl ) ethoxycarbonyl , - 3 -( trimethylsilyl ) ethoxymethyl , - triphenylsilyl or - trityl . wherein the chiral centers may be ( r ) or ( s ) configuration ; l is halogen , alkylsulfonyloxy , perfluoroalkylsulfonyloxy , arylsulfonyloxy , substituted alkylsulfonyloxy or substituted arylsulfonyloxy ; and r is h , alkyl , aryl , aralkyl , heteroaryl , heterocyclic . wherein the chiral centers may be ( r ) or ( s ) configuration ; l is halogen , alkylsulfonyloxy , perfluoroalkylsulfonyloxy , arylsulfonyloxy , substituted alkylsulfonyloxy , or substituted arylsulfonyloxy ; and r is h , alkyl , aryl , aralkyl , heteroaryl , or heterocyclic . typically , radiopharmaceutical products comprise two functional components , one being radioactive and the other not being radioactive . the radioactive component makes possible the detection of the product in the context of the theranosis ( diagnosis + therapy ) and it constitutes the active agent in the case of therapeutic use . it is a radionuclide with appropriate physical properties . the nonradioactive component , for its part , is a molecule or tracer , intended to accumulate in the target organ , tissue , tumor and / or site , and the like , to ensure the accumulation of radioactivity . in one aspect of the present invention , there is provided precursors / synthons useful for the production of molecules ( such as radiochemical compounds ) for imaging , detection , diagnosis , chemotherapy , radiochemotherapy , and molecular radiotherapy ( mrt ) of disease in a subject . in one example , the radiolabelled compounds are useful for detecting hypoxic conditions present in , e . g ., tissues of the brain , head and neck , lungs , heart , eyes , kidney , liver , pancreas , thymus , intestines , urogenital organs , stomach , skin , and bone . the hypoxic conditions can result from ischemia ( e . g ., as a result of stroke ), inflammation , wound healing , and cancer . in another example , the radiolabelled compounds will contain a therapeutic radionuclide ( e . g ., 131 / 124 / 125 i ) which will provide self - sensitizing low doses of the radiation to kill the tumor cells . these compounds will be useful for molecular radiotherapy ( mrt ) of hypoxic tumors . the term “ radiochemical ” as used herein includes any organic , inorganic or organometallic compound comprising a covalently - attached radioactive diagnostic or therapeutic isotope , any coordinated radioactive ligand or isotope for diagnosis and therapy , any inorganic radioactive ionic solution , any superparamagnetic naonparticle - linked ( substituted or linked ) molecule - attached with radioactive diagnostic or therapeutic molecule , or any radioactive gas , including radioactive molecular imaging probes intended for administration to a patient ( e . g ., by inhalation , ingestion or intravenous injection ) for tissue imaging and / or radiotherapy purposes for killing the hypoxic tumor cells , which are also referred to in the art as radiopharmaceuticals , radiotracers , radioligands or radiotherapeutics . the term “ radioactive isotope ” or “ radioactive element ” as used herein , refers to isotopes undergoing radioactive decay ( e . g ., emitting radiation ) and radiolabeling agents comprising a radioactive isotope . such isotopes or elements are also referred to in the art as radioisotopes or radionuclides . the precursors of the present invention contain nucleophilically substitutable moieties that can be chemically reacted to incorporate a variety of short - lived radionuclides such as radiohalogens , e . g . f - 18 , radioiodines ( i - 123 / 124 / 125 / 131 ), carbon - 11 , and long lived radioisotopes e . g ., h - 3 , c - 14 and s - 35 etc . the synthesis process for the class of the molecules ( containing naturally abundant isotopes or corresponding radioisotopes ) described herein may involve a conventional thermal chemistry process or a non - conventional process e . g . using microwave ( mw ) chemistry or a microfluidic process , but not limited to these synthesis techniques . the processes of the present application can also be adapted to develop processor - controlled automated synthesis processes where sequential release of the reagents to the reactor , reaction parameters e . g ., temperature , duration , amounts of various reagents , and the purification process will be controlled by a software , or combination of software . in one example of the present invention , one class of the compounds ( 2 - nitroimidazole based sugar - coupled molecules ) was evaluated , and was found to provide superior ( radio ) chemical yields , fewer secondary products , and a cleaner radiolabeling profile in comparison to the existing precursors . the radiochemicals produced using the compositions and methods of the present application are suitable for use in a number of diseases , including but not limited to , oncological disorders , diabetes , inflammatory disorders and stroke . methods of the present invention are conveniently practiced by providing the compound ( s ) and / or composition ( s ) used in such method in the form of a kit . such a kit preferably contains the instructions of the use thereof . in one example , there is provided a kit for the manufacture of an imaging agent , comprising : a compound as described herein ; and instructions for the use thereof . in one example , said imaging , chemotherapy or radiotherapy agent is faza or iaza . in one example , said imaging agent , chemotherapy or radiotherapy is suitable for manufacture using an automated radio - synthesis unit . all chemicals used were , purchased from sigma - aldrich co ., usa , were reagent grade , and used without any further purification . solvents were dried over appropriate drying agents and freshly distilled before use . the progress of synthetic reactions was monitored by thin layer chromatography ( tlc ; 90 : 10 , v / v , solvent system b ) or hexanes : etoac ( 7 : 1 , v / v , solvent system c ; 3 : 2 , v / v , solvent system d and 1 : 1 , v / v , solvent system e ) as developing solvents . column chromatography was performed on merck silica gel 60 ( particle size 70 - 200 and 230 - 400 mesh astm ). melting points were determined on a büchi capillary melting point apparatus and are uncorrected . 1 h and 13 c nmr spectra were recorded on a bruker am - 300 spectrometer in deuterated chloroform ( cdcl 3 ) or deuterated methanol ( cd 3 od ), depending on the solubility of the product . chemical shifts are reported in ppm downfield with respect to tetramethylsilane as an internal standard . the 1 h nmr assignments were confirmed by selective decoupling experiments . the 13 c nmr resonances are assigned by using the j modulation spin echo technique to determine the number of hydrogen atoms attached to each carbon atom . the protons and carbons of the sugar moiety and nitroimidazole are represented by a single prime (′) and no prime , respectively . when necessary , high resolution mass spectra ( hrms ) were recorded using an aei - ms - 12 mass spectrometer . tr19 negative ion accelerating cyclotron capable of accelerating protons to 19 mev and deuterons to 9 . 5 mev ( advanced cyclotron systems , inc .) with an external high performance multicusp ion source greater than 150 μa beam current with dual simultaneous beam extraction was used for 18 f production . the radiofluoride target consisting of a niobium body with havar foil window was used for production of 18 f via 18 o ( p , n ) 18 f reaction by irradiating highly 18 o enriched water ( h 2 18 o ). tracerlab fx automated synthesis units ( asu ) employed for the manufacture of 18 f - faza was purchased from g . e . medical technologies inc ., canada which operates on the basis of performing unit operations under computer ( cpu ) control , involving the movement of liquids , movement of gases ( vacuum , pressure ), valve actuation and heating systems on a time dependent basis through a well defined flow path . feedback control , monitoring and diagnostic functions are built into the operation using various sensor - based systems . 1 - α - d -( 5 ′- o -( 4 - nitrobenzenesulfonyl )- 2 ′, 3 ′- di - o - acetyl - arabinofuranosyl )- 2 - nitroimidazole ( diacetyl aza nosylate , 3 ), 1 - α - d -( 5 ′- o -( 4 - nitrobenzenesulfonyl )- 2 ′, 3 ′- di - o - pivaloyl - arabinofuranosyl )- 2 - nitroimidazole ( dipivaloyl aza nosylate , 3a ), 1 - α - d -( 5 ′- o -( toluenesulfonyl )- 2 ′, 3 ′- di - o - pivaloyl - arabinofuranosyl )- 2 - nitroimidazole ( dipivaloyl aza tosylate , 8 ), and their precursors were synthesized under the general formula 1 this compound was synthesized by three methods a , b and c . nosyl chloride ( 0 . 674 g , 3 . 04 mmol ) was added to a stirred pre - cooled solution of 2 ′, 3 ′- di - o - acetyl aza , 2 , ( 0 . 5 g , 1 . 52 mmol ) in anhydrous pyridine ( 8 ml ) at 0 ° c . under an atmosphere of argon . the stirring was continued for 3 h at this temperature , and then for an additional 1 h at 22 ° c . the progress of the reaction was quenched by adding a piece of ice , the solvents were evaporated under reduced pressure and the crude product was dissolved in ethyl acetate ( 5 ml ) and washed with water ( 3 × 5 ml ). the organic layer was dried ( mgso 4 ) and evaporated under reduced pressure to give 0 . 75 g of impure product . the crude material was purified by flash silica gel column chromatography ( hexanes : etoac ; 1 : 2 ; v / v ) to give pure diacetyl aza nosylate , compound 3 , as white foam . in addition , this reaction also afforded 5 ′- chloro - 5 ′- deoxy - 2 ′, 3 ′- di - o - acetyl aza , as white foam which was recrystallized from ether / hexane ( 5 ml , 1 : 1 , v / v ) to give white crystals . the characterization data for these compounds are provided below . yield 0 . 23 g ( 29 %); thermal softening , 49 - 51 ° c . ; rf 0 . 63 ( 5 % meoh in chcl 3 ); 1 h nmr ( cdcl 3 ): 2 . 02 and 2 . 22 ( two s , each for 3h , two acetyl )), 4 . 37 and 4 . 43 ( two dd , j 5 ′, 4 ′ = 2 . 4 hz , j 5 ″, 4 ′ = 4 . 6 hz , and j gem = 12 . 8 hz , 2h , h - 5 ′ and h - 5 ″), 4 . 54 ( ddd , j 3 ′, 4 ′ = j 5 ′, 4 ′ = 2 . 4 hz , j 5 ″, 4 ′ = 4 . 6 hz 1h , h - 4 ′), 5 . 13 ( d , j 3 ′, 2 ′ = 1 . 8 hz , 1h , h - 3 ′), 5 . 45 ( s , 1h , h - 2 ′), 6 . 61 ( s , 1h , h - 1 ′), 7 . 22 ( s , 1h , imidazole h - 4 ), 7 . 29 ( s , 1h , imidazole h - 5 ), 8 . 17 ( dd , j 2 , 3 = j 6 , 5 = 8 . 8 hz , j 5 , 3 = j 6 , 2 = 1 . 8 hz , 2h , h - 3 and h - 5 of phenyl ), and 8 . 44 ( dd , j 3 , 2 = j 5 , 6 = 8 . 9 hz , j 3 , 5 = j 2 , 6 = 1 . 8 hz , 2h , h - 2 and h - 6 of phenyl ) ppm ; 13 c nmr ( cdcl 3 ) δ 20 . 27 ( 2 × ch 3 ), 68 . 56 ( c - 5 ′), 76 . 21 ( c - 4 ′), 80 . 81 ( c - 3 ′), 84 . 75 ( c - 2 ′), 92 . 91 ( c - 1 ′), 121 . 77 ( imidazole c - 4 ), 124 . 52 ( phenyl c - 3 and c - 5 ), 128 . 54 ( imidazole c - 5 ), 129 . 30 ( phenyl c - 2 and c - 6 ), 141 . 02 ( phenyl c - 4 ), 143 . 91 ( imidazole c — no 2 ), 150 . 95 ( phenyl c - 1 ), 168 . 68 ( c ═ o at c - 2 ′), 169 . 28 ( c ═ o at c - 3 ′) ppm ; analysis for c 18 h 18 n 4 o 12 s calc . c , 42 . 03 ; h , 3 . 53 ; n , 10 . 89 . found c , 42 . 16 ; h , 3 . 58 ; n , 10 . 47 ; hrms ( ei ) for c 18 h 18 n 4 o 12 sna calc . 537 . 05341 ; found 537 . 05329 ( m + 94 . 18 %); analysis for c 18 h 18 n 4 o 12 s calc . c , 41 . 45 ; h , 4 . 06 ; n , 12 . 08 . found c , 42 . 03 , h , 3 . 53 , n , 10 . 89 ; hrms ( ei )— c 18 h 18 n 4 o 12 s . calc . 514 . 42 ; found 514 . 06 . yield 0 . 29 g ( 55 %); mp 129 - 131 ° c . ; rf 0 . 71 ( 5 % meoh in chcl 3 ); 1 h nmr ( cdcl 3 ): 2 . 02 and 2 . 22 ( two s , each for 3h , two acetyl )), 4 . 37 and 4 . 43 ( two dd , j 5 ′, 4 ′ = 2 . 4 hz , j 5 ″, 4 ′ = 4 . 8 hz , and j gem = 12 . 8 hz , 2h , h - 5 ′ and h - 5 ″) 4 . 54 ( ddd , j 3 ′, 4 ′ = j 5 ′, 4 ′ = 2 . 4 hz , j 5 ″, 4 ′ = 4 . 8 hz 1h , h - 4 ′), 5 . 13 ( d , j 3 ′, 2 ′ = 1 . 8 hz , 1h , h - 3 ′), 5 . 45 ( s , 1h , h - 2 ′), 6 . 61 ( d , j 2 ′, 1 ′ = 1 . 2 hz , 1h , h - 1 ′), 7 . 22 ( s , 1h , imidazole h - 4 ), 7 . 29 ( s , 1h , imidazole h - 5 ), 8 . 17 ( dd , j 2 , 3 = j 6 , 5 = 6 . 7 hz , j 5 , 3 = j 6 , 2 = 1 . 8 hz , 2h , h - 3 and h - 5 of phenyl ), and 8 . 44 ( dd , j 3 , 2 = j 5 , 6 = 6 . 7 hz , j 3 , 5 = j 2 , 6 = 1 . 8 hz , 2h , h - 2 and h - 6 of phenyl ) ppm ; 13 c nmr ( cdcl 3 ) δ 20 . 46 and 20 . 51 ( two ch 3 ), 38 . 77 ( carbon of tert - butyl at c - 3 ′), 68 . 52 ( c - 5 ′), 76 . 17 ( c - 4 ′), 80 . 80 ( c - 3 ′), 84 . 85 ( c - 2 ′), 93 . 01 ( c - 1 ′), 121 . 81 ( imidazole c - 4 ), 124 . 55 ( phenyl c - 3 and c - 5 ), 128 . 53 ( imidazole c - 5 ), 129 . 35 ( phenyl c - 2 and c - 6 ), 140 . 98 ( phenyl c - 4 ), 143 . 91 ( imidazole c — no 2 ), 150 . 95 ( phenyl c - 1 ), 168 . 76 ( c ═ o at c - 2 ′), 169 . 35 ( c ═ o at c - 3 ′) ppm ; analysis for c 12 h 14 cln 3 o 7 calc . c , 41 . 45 ; h , 4 . 06 ; n , 12 . 08 ; cl , 10 . 20 . found c , 41 . 73 ; h , 3 . 84 ; n , 11 . 90 ; cl , 10 . 16 . a solution of 5 ′- chloro - 5 ′- deoxy - aza ( 0 . 20 g , 0 . 575 mmol ) in methanolic ammonia ( 2m , 5 ml ) was stirred at 22 ° c . for 16 h and then the solvent was evaporated under reduced pressure using a rotary evaporator . the residue was purified by a flash silica gel column chromatography using 5 % meoh in ch 2 cl 2 as an eluent . the process afforded a colorless oil which was recrystallized from ether / hexane ( 2 : 1 , 15 ml ) to give white crystals . yield 0 . 15 g ( 96 %); mp 133 - 135 ° c . ; rf 0 . 29 ( 5 % meoh in ch 2 cl 2 ); 1 h nmr ( cdcl 3 ): 3 . 75 ( dd , j 5 ′, 4 ′ = 6 . 6 hz , j gem = 14 . 2 hz , 1h , h - 5 ′), 3 . 80 ( dd , j 5 ″, 4 ′ = 7 . 3 hz , j gem = 13 . 2 hz , 1h , h - 5 ″), 4 . 19 ( d , j 4 ′, 3 ′ = 1 . 1 hz , 1h , h - 3 ′), 4 . 28 ( s , 1h , h - 2 ′), 4 . 60 ( ddd , j 3 ′, 4 ′ = 1 . 1 hz , j 5 ′, 4 ′ = 6 . 6 hz , j 5 ″, 4 ′ = 7 . 3 hz 1h , h - 4 ′); 6 . 45 ( s , 1h , h - 1 ′), 7 . 12 ( s , 1h , imidazole h - 4 ), 7 . 65 ( s , 1h , imidazole h - 5 ) ppm ; 13 c nmr ( cd 3 od ) δ 44 . 63 ( c - 5 ′), 78 . 51 ( c - 4 ′), 83 . 65 ( c - 3 ′), 90 . 93 ( c - 2 ′), 97 . 25 ( c - 1 ′), 125 . 26 ( imidazole c - 4 ), 128 . 04 ( imidazole c - 5 ), 145 . 19 ( imidazole c — no 2 ) ppm ; analysis for c 8 h 10 cln 3 o 5 ( 263 . 63 ) calc . c , 36 . 45 ; h , 3 . 82 ; n , 15 . 94 ; cl , 13 . 45 . found c , 36 . 70 ; h , 3 . 77 ; n , 15 . 54 , cl , 13 . 37 . silver 4 - nitrobenzenesulfonate ( 186 mg , 0 . 6 mmol ) was dissolved in anhydrous acetonitrile ( 1 ml ) and the mixture was added to diacetyl iaza ( 88 mg , 0 . 2 mmol ) in a capped vial and stirred vigorously at 60 ° c . for 4 hours . the tlc analysis of the reaction mixture at this time showed the exhaustion of diacetyl iaza and the formation of 3 . the reaction mixture was filtered and the solvent was evaporated under reduced pressure . the residue , so obtained , was purified by flash silica gel column chromatography using etoac / toluene ( 1 : 1 ; v / v ) as an eluent to afford 3 as a foam 42 mg . ( yield 40 %). proton and carbon nmr data for 3 , obtained using method b were same as those obtained by method a . 4 - nitrobenzenesulfonyl ( nosyl ) chloride ( 135 mg , 0 . 6 mmol ) in pyridine ( 0 . 5 ml ) was added to a stirred solution of α - aza , 1 , ( 150 mg , 0 . 62 mmol ) in pyridine ( 2 ml ) at − 15 ° c . the reaction was left to stir overnight at − 5 ° c . this was followed by the addition of acetic anhydride ( 33 mg , 3 . 0 mmol ). the reaction mixture was stirred for another 4 h at 22 ° c ., and then worked up . removal of the solvents at the reduced pressure , followed by a flash column chromatography of the impure material afforded pure 3 ( 193 mg , 60 %). the analytical data for compound 3 , obtained by this method corresponded to the data obtained by methods a and b as described above . the synthesis of compound 3a was achieved by two methods a and b as shown in scheme 1 , and is described below . tert - butyl diphenylchlorosilane ( 0 . 25 ml , 0 . 97 mmol ) was added drop wise to a solution of aza ( 260 mg , 1 . 06 mmol ) in 1 . 25 ml of pyridine . follow the reaction mixture was stirred at room temperature for 24 h , trimethylacetyl chloride ( 0 . 5 ml , 4 . 05 mmol ) was added dropwise . after the reaction mixture was stirred at room temperature for another 48 h , all solvents were evaporated in vacuo . the residue was purified by sio 2 column chromatography using etoac / hexanes ( 1 : 4 , v / v ) as eluents to afford 1a ( 513 mg ) as colorless syrup . 1 h - nmr ( cdcl 3 , 300 mhz ) δ 7 . 73 ˜ 7 . 67 ( m , 4h , phenyl ), 7 . 47 ˜ 7 . 36 ( m , 6h , phenyl ), 7 . 23 ( d , j 4 , 5 = 1 . 0 hz , 1h , h - 5 ), 7 . 22 ( d , j 5 , 4 = 1 . 0 hz , 1h , h - 4 ), 6 . 46 ( d , j 2 ′, 1 ′ = 1 . 3 hz , 1h , h - 1 ′), 5 . 27 ( d , j 1 ′, 2 ′ = 1 . 3 hz , 1h h - 2 ′), 5 . 14 ( dd , j 2 ′, 3 ′ = 1 . 0 hz , j 4 ′, 3 ′ = 2 . 1 hz , 1h , h - 3 ′), 4 . 52 ( ddd , j 3 ′, 4 ′ = 2 . 1 hz , j 5 ′, 4 ′ = 5 . 0 hz , j 5 ″, 4 ′ = 5 . 0 hz , 1h , h - 4 ′), 3 . 89 ( dd , j 4 ′, 5 ′= 5 . 0 hz , j gem = 11 . 0 hz , 1h , h - 5 ′), 3 . 83 ( dd , j 4 ′, 5 ′ = 5 . 0 hz , j gem , 11 . 0 hz , 1h , h ′- 5 ′), 1 . 12 ( s , 9h , 3 × ch 3 ), 1 . 10 ( s , 9h , 3 × ch 3 ), 1 . 09 ( s , 9h , 3 × ch 3 ) ppm ; 13 c - nmr ( cdcl 3 , 75 mhz ) δ 176 . 6 ( c ═ o ), 176 . 1 ( c ═ o ), 146 . 0 ( c - 2 ), 135 . 7 - 132 . 9 ( phenyl carbons ), 129 . 9 ( c - 5 ), 127 . 8 ˜ 127 . 7 ( remaining phenyl carbons ), 123 . 3 ( c - 4 ), 92 . 3 ( c - 1 ′), 88 . 1 ( c - 2 ′), 81 . 4 ( c - 3 ′), 77 . 4 ( c - 4 ′), 63 . 6 ( c - 5 ′), 38 . 6 ( c ( ch 3 ) 3 ), 26 . 9 ( ch 3 ), 19 . 3 ( sic ( ch 3 ) 3 ) ppm . compound 1a ( 500 mg , 0 . 8 mmol ) was dissolved in of acetonitrile ( 25 ml ), then benzoic acid ( 658 . 4 mg , 5 . 6 mmol ) and potassium fluoride ( 325 . 8 mg , 5 . 6 mmol ) were added to this solution . the reaction mixture was stirred at 80 ° c . for 12 h . the mixture was filtered and the solution was evaporated in vacuo . the residue was purified with sio 2 column chromatography using etoac / hexanes ( 1 : 2 , v / v ) as eluent to afford 2a ( 220 mg ) as syrup . 1 h - nmr ( cdcl 3 , 300 mhz ) δ 7 . 39 ( d , j 4 , 5 = 1 . 0 hz , 1h , h - 5 ), 7 . 23 ( d , j 5 , 4 = 1 . 0 hz , 1h , h - 4 ), 6 . 65 ( d , j 2 ′, 1 ′ = 1 . 0 hz , 1h , h - 1 ′), 5 . 37 ( d , j 1 ′, 2 ′ = 1 . 0 hz , 1h , h - 2 ′), 5 . 04 ( dd , j 2 ′, 3 ′ = 1 . 0 hz , j 4 ′, 3 ′ = 2 . 1 hz , 1h , h - 3 ′), 4 . 52 ( ddd , j 3 ′, 4 ′ = 2 . 1 hz , j 5 ′, 4 ′ = 5 . 3 hz , j 5 ″, 4 ′ = 5 . 3 hz , 1h , h - 4 ′), 3 . 94 ( dd , j 4 ′, 5 ′ = 5 . 3 hz , j gem = 9 . 0 hz , 1h , h - 5 ′), 3 . 90 ( dd , j 4 ′, 5 ″ = 5 . 3 hz , j gem = 9 . 0 hz , 1h , h ′- 5 ′), 2 . 42 ( s , 1h , oh ), 1 . 28 ( s , 9h , 3 × ch 3 ), 1 . 10 ( s , 9h , 3 × ch 3 ) ppm ; 13 c - nmr ( cdcl 3 , 75 mhz ) δ 177 . 3 ( c ═ o ), 176 . 3 ( c ═ o ), 146 . 0 ( c - 2 ), 129 . 9 ( c - 5 ), 123 . 3 ( c - 4 ), 93 . 2 ( c - 1 ′), 88 . 9 ( c - 2 ′), 81 . 7 ( c - 3 ′), 77 . 4 ( c - 4 ′), 62 . 4 ( c - 5 ′), 38 . 7 ( c ( ch 3 ) 3 ), 26 . 9 ( ch 3 ) ppm . compound 2a ( 210 mg , 0 . 5 mmol ) was dissolved in 10 ml of pyridine , 4 - nitrobenzenesulfonyl chloride ( 221 mg , 1 mmol ) and dmap ( 6 mg , 0 . 05 mmol ) was added . the reaction mixture was stirred at room temperature for 16 h . the solvent was evaporated in vacuum . the residue was purified by sio 2 column chromatography using etoac / hexanes 1 : 4 ( v / v ) as eluent to afford 65 mg of 3a as syrup . 1 h - nmr ( cdcl 3 , 300 mhz ) δ 8 . 43 ( d , j 3 ″, 2 ″ = j 5 ″, 6 ″ = 6 . 72 hz , 2h , phenyl h - 2 ″, h - 6 ″), 8 . 17 ( d , j 2 ″, 3 ″ = j 6 ″, 5 ″ = 6 . 72 hz , 2h , phenyl h - 3 ″, h - 5 ″), 7 . 30 ( s , 1h , h - 5 ), 7 . 23 ( s , 1h , h - 4 ), 6 . 61 ( d , j 2 ′, 1 ′ = 1 . 2 hz , 1h , h - 1 ′), 5 . 39 ( d , j 1 ′, 2 ′ = 1 . 2 hz , 1h , h - 2 ′), 4 . 99 ( dd , j 2 ′, 3 ′ = 1 . 2 hz , j 4 ′, 3 ′ = 2 . 4 hz , 1h , h - 3 ′), 4 . 62 ( ddd , j 3 ′, 4 ′ = 2 . 4 hz , j 5 ′, 4 ′ = 5 . 5 hz , j 5 ″, 4 ′ = 5 . 5 hz , 1h , h - 4 ′), 4 . 42 ( dd , j 4 ′, 5 ′ = 5 . 5 hz , j gem = 11 . 0 hz , 1h , h - 5 ′), 4 . 39 ( dd , j 4 ′, 5 ″ = 5 . 5 hz , j gem = 11 . 0 hz , 1h , h ′- 5 ′), 1 . 28 ( s , 9h , 3 × ch 3 ), 1 . 10 ( s , 9h × ch 3 ) ppm ; 13 c nmr ( cdcl 3 ) δ 26 . 82 and 26 . 86 ( ch 3 s from pivaloyl moieties ), 38 . 63 and 38 . 82 ( tert - c in pivaloyl moities ), 68 . 43 ( c - 5 ′), 76 . 26 ( c - 4 ′), 81 . 06 ( c - 3 ′), 85 . 08 ( c - 2 ′), 93 . 30 ( c - 1 ′), 122 . 00 ( imidazole c - 4 ), 124 . 54 ( phenyl c - 3 and c - 5 ), 124 . 58 ( imidazole c - 5 ), 129 . 38 ( phenyl c - 2 and c - 6 ), 141 . 18 ( phenyl c - 1 and imidazole c - 2 ), 151 . 02 ( phenyl c - 1 ), 176 . 17 ( c ═ o at c - 2 ′), 177 . 08 ( c ═ o at c - 3 ′) ppm . this route included the reaction of silver nosylate with 1 - α - d -[ 5 ′- iodo - 2 ′, 3 ′- di - o - trimethylacetylarabinofuranosyl ]- 2 - nitroimidazole ( di - pivaloyl iaza ), 6 ( the synthesis for 6 is described under example ii ), and proceeded as below . silver 4 - nitrobenzene sulfonate ( 3 . 01 g , 9 . 74 mmol ) was dissolved in anhydrous acetonitrile ( 30 ml ) and the mixture was added to dipivaloyl iaza ( 1 . 5 g , 2 . 87 mmol ), pre - contained in a round bottom flask , and the contents were stirred vigorously at 60 ° c . for 4 h . the reaction mixture was then filtered and the solvent was removed by rotary evaporation under reduced pressure . the residue was purified by flash silica gel column chromatography using ethyl acetate / hexanes ( v / v ; 1 : 3 ) to afford pure 3a ( 55 mg ) as syrupy product along with unreacted dipivaloyl iaza ( 1 . 0 g ). this molecule was synthesized by methods a and c as described below . 1 - α - d -[ 5 ′- hydroxyl - 2 ′, 3 ′- di - o - trimethylacetylarabinofuranosyl ]- 2 - nitroimidazole , 2a , ( 200 mg , 0 . 5 mmol ) was dissolved in anhydrous pyridine ( 20 ml ), stirred , and cooled to 0 - 5 ° c . toluenesulfonylchloride ( 105 mg , 0 . 55 mmol ) was added to it , and the contents were stirred . the temperature was allowed to warm up to 22 ° c ., and the stirring was continued for an additional 24 h . ice ( 3 ml ) was added , and the solvents were evaporated under reduced pressure to afford impure mixture , which was chromatographed on a flash silica gel column ( 0 . 25 % meoh in ch 2 cl 2 ) to give 0 . 19 g ( 69 %) of pure tsdipiv - aza as white crystals ( m . p . 55 - 57 ° c . ); 1 h nmr ( cdcl 3 ) δ 1 . 09 ( s , 9h , t - butyl group ), 1 . 25 ( s , 9h , t - butyl group ), 2 . 46 ( s , 3h , toluoyl ch 3 ), 4 . 24 ( dd , j 4 , 5 ′ = 2 . 4 hz , j gem = 7 . 3 hz , 1h , h - 5 ′), 4 . 28 ( dd , j 5 ″, 4 ′ = 4 . 5 hz , j gem = 7 . 3 hz , 1h , h - 5 ″), 4 . 63 ( ddd , j 3 ′, 4 ′ = 1 . 6 , j 5 ′, 4 ′ = 2 . 4 hz , j 5 ″, 4 ′ = 4 . 5 hz , 1h , h - 4 ′), 4 . 98 ( d , j 4 ′, 3 ′ = 1 . 6 hz , 1h , h - 3 ′), 5 . 33 ( s , 1h , h - 2 ′), 6 . 51 ( s , 1h , h - 1 ′), 7 . 22 ( s , 1h , imidazole h - 4 ), 7 . 31 ( s , 1h , imidazole h - 5 ), 7 . 38 ( d , 2h , j = 8 . 2 hz , phenyl h - 3 and h - 5 ), 7 . 83 ( d , 2h , j = 8 . 2 hz , phenyl h - 2 and h - 6 ) ppm ; 13 c nmr ( cdcl 3 ) δ 21 . 69 ( tolyl ch 3 ), 26 . 83 and 26 . 87 ( 6 × ch 3 , two tert - butyl ), 38 . 59 and 38 . 77 ( 2 × carbons of tert - butyl ), 67 . 71 ( c - 5 ′), 76 . 32 ( c - 4 ′), 81 . 15 ( c - 3 ′), 85 . 20 ( c - 2 ′), 93 . 31 ( c - 1 ′), 121 . 76 ( imidazole c - 4 ), 128 . 03 ( phenyl c - 3 and c - 5 ), 128 . 53 ( imidazole c - 5 ), 129 . 96 ( phenyl c - 2 and c - 6 ), 132 . 44 ( c - 1 phenyl ), 145 . 36 ( c - 2 , nitroimidazole ), 145 . 36 ( c , phenyl c - 4 ), 176 . 05 ( c ═ o at c - 2 ′), 176 . 76 ( c ═ o at c - 3 ′) ppm . hplc retention time : 50 % ch 3 cn / 50 % h 2 o ; 1 . 5 ml / min : 280 nm ; 19 . 02 minutes . 1 - α - d -( 5 ′- o - toluenesulfonylarabinofuranosyl )- 2 - nitroimidazole ( 7 ). toluenesulfonyl ( tosyl ) chloride ( 78 . 3 mg , 0 . 41 mmol ) in pyridine ( 0 . 5 ml ) was added to a stirred solution of α - aza , 1 , ( 100 mg , 0 . 41 mmol ) in pyridine ( 2 ml ) at − 15 ° c . the reaction was left to stir overnight at − 5 ° c . a second addition of tosyl chloride ( 40 mg , 0 . 21 mmol ) in pyridine ( 0 . 5 ml ) was added again at − 15 ° c . and left to stir at 5 ° c . overnight . ice ( 3 ml ) was added then the solution was evaporated under reduced pressure to remove the pyridine . the crude product was dissolved in ethyl acetate ( 10 ml ) and washed with water ( 3 × 10 ml ). the organic layer was dried ( mgso 4 ) and evaporated under reduced pressure to give 0 . 17 g of impure product which was purified by flash column chromatography ( 0 . 75 % meoh in ch 2 cl 2 ) to give 0 . 09 g ( 55 %) of pure tosyl - aza as white crystals ; 1 h nmr ( cdcl 3 ) δ 2 . 45 ( s , 3h , tolyl ch 3 ), 4 . 00 ( m , 1h , h - 4 ′), 4 . 22 ( m , 2h , h - 5 ′), 4 . 90 ( s , 2h , h - 2 ′ and h - 3 ′), 6 . 26 ( s , 1h , h - 1 ′), 7 . 10 ( s , 1h , imidazole h - 4 ), 7 . 93 ( d , 2h , phenyl h - 3 and h - 5 , j = 8 . 0 hz ), 7 . 58 ( s , 1h , imidazole h - 5 ), 7 . 82 ( d , 2h , phenyl h - 2 and h - 6 , j = 8 . 0 hz ) ppm . 1 - α - d -( 5 ′- o - toluenesulfonyl - 2 ′, 3 ′- di - o - trimethylacetylarabinofuranosyl )- 2 - nitroimidazole ( tsdipiv - aza , dipivaloyl aza tosylate , pivaloyl tosyl aza , pivaloyl aza tosylate ; 8 ). trimethylacetyl ( pivaloyl ) chloride ( 60 . 2 mg , 61 . 5 μl , 0 . 50 mmol , 2 . 5 eq ) was added to a stirred solution of 7 , ( 80 . 0 mg , 0 . 20 mmol ) in pyridine ( 3 ml ) at − 15 ° c . the reaction was left to stir overnight at − 5 ° c . a second addition of trimethylacetyl chloride ( 12 . 0 mg , 12 . 3 ml , 100 μmol ) was again added at − 15 ° c . and left to stir at − 5 ° c . for 24 hours . ice ( 3 ml ) was added then the solution was evaporated under reduced pressure to remove the pyridine . the crude product was dissolved in ethyl acetate ( 5 ml ) and washed with water ( 3 × 5 ml ). the organic layer was dried ( mgso 4 ) and evaporated under reduced pressure to give 0 . 90 g of crude product . the crude material was purified by flash column chromatography ( 0 . 25 % meoh in ch 2 cl 2 ) to give 0 . 070 g ( 62 %) of pure tsdipiv - aza as white crystals . the analytical and spectral data for 8 obtained by this method corresponded to the data obtained by method a , and confirmed the formation of this compound . 1 - α - d -( 5 ′- iodo - 5 ′- deoxyarabinofuranosyl )- 2 - nitroimidazole ( α - iaza ) ( 1 . 10 g , 2 . 88 mmol ) was dissolved in pyridine ( 100 ml ) and trimethylacetyl chloride ( 2 . 7 g , 14 . 1 mmol ) was added drop wise to this solution under stirring . the mixture was stirred at room temperature for 30 h , and then the solvent was removed in vacuo . the viscous residue , so obtained , was purified by flash silica gel column chromatography using ethyl acetate / hexanes ( 1 : 4 ; v / v ) to afford pure product as syrup . yield 1 . 49 g . ( 90 %); 1 h - nmr ( cdcl 3 , 300 mhz ) δ 7 . 39 ( d , j 4 , 5 = 1 . 2 hz , 1h , h - 5 , imidazole ), 7 . 23 ( d , j 5 , 4 = 1 . 2 hz , 1h , h - 4 , imidazole ), 6 . 67 ( d , j 2 ′, 1 ′ = 1 . 2 hz , 1h , h - 1 ′), 5 . 37 ( d , j 2 ′, 1 ′ = 1 . 2 hz , 1h , h - 2 ′), 5 . 16 ( dd , j 2 ′, 3 ′ = 1 . 2 hz , j 4 ′, 3 ′ = 1 . 8 hz , 1h , h - 3 ′), 4 . 65 ( ddd , j 3 ′, 4 ′ = 1 . 8 hz , j 5 ′, 4 ′ = 7 . 3 hz , j 5 ′, 4 ′ = 7 . 3 hz , 1h , h - 4 ′), 3 . 47 ( dd , j 4 ′, 5 ′ = 7 . 3 hz , j gem = 11 . 0 hz , 1h , h - 5 ′), 3 . 41 ( dd , j 4 ′, 5 ″ = 7 . 3 hz , j gem = 11 . 0 hz , 1h , h ′- 5 ′) ppm ; 13 c - nmr ( cdcl 3 , 75 mhz ) δ 176 . 6 ( c ═ o ), 175 . 9 ( c ═ o ), 148 . 0 ( c - 2 ), 130 . 1 ( c - 5 ), 123 . 3 ( c - 4 ), 93 . 4 ( c - 1 ′), 87 . 7 ( c - 2 ′), 81 . 5 ( c - 3 ′), 78 . 1 ( c - 4 ′), 38 . 6 ( c - 5 ′), 26 . 9 ( ch 3 ), 2 . 10 ( c ( ch 3 ) 3 ) ppm . radiofluorination was performed in a ge tracerlab fdg fx ™ automated synthesizer . 18 f - fluoride was delivered from the target on to a qma accel trapping cartridge , preconditioned with 0 . 5 m nahco 3 , and was trapped as na 18 f . elution of this fluoride was done by a solution of k 2 co 3 / k2 . 2 . 2 solution ( 3 . 5 mg : 15 mg in 100 μl h 2 o / 900 μl anhydrous acetonitrile , respectively ) followed by two azeotropic dryings of this complex at 70 ° c . using acetonitrile . the aza precursor , under investigation , was dropped in to the reactor as a solution in anhydrous dmso ( 1 . 0 ml ) and , depending on the precursor , was reacted at 100 ° c . for 5 - 10 min . this was followed by the removal of protective groups ( acetyl or pivaloyl ) from the radiofluorinated intermediate by alkaline hydrolysis using 0 . 1n naoh solution for 2 min at 30 ° c . the ph of the reaction mixture was neutralized by adding 0 . 9 ml of 0 . 4m nah 2 po 4 aqueous solution and the whole mixture was dispensed to the hplc injector ( 7 ml loop size ) for the chromatographic purification . post - labeling mixture was subjected to hplc purification process . the instrumentation , control systems and connections used for this process consisted of beckman “ gold plus ” integrated pumps / model number 126 and beckman 32 karat / version 3 . 0 software , hplc rp phenomenex nucleosil 10μ c 18 100 a column ( 25 × 1 . 0 cm ) and a phenomenex luna 5μ c 18 100 a column ( 5 . 0 × 1 . 0 cm ). eluent for hplc purification , composed of 8 % ethanol and 92 % sterile water for injection ( swfi ), was run at a flow rate of 2 . 0 ml / min . radiolabeled 18 f - faza was identified by a dual detection technique that used uv absorption ( λmax 320 ηm ) and corresponding radioactive peak at same retention time . the radiochemical identity of the peak corresponding to 18 f - faza was confirmed by injecting standard faza prior to the purification of radiolabeled mixture under same elution conditions that appeared at a retention time of 26 (± 5 %). impure labeled mixture was also checked by tlc ‘ co - spot ’ chromatography ( 2 . 5 × 7 . 5 silica gel micro tlc plates using etoac as developing solvent ) to obtain exact composition of the radiochemical mixture and determine the losses that happen during the hplc purification . the radiochemical identity and the purity of purified 18 f - faza were confirmed by tlc chromatography . a tlc plate was spotted with standard faza ( left ), a co - spot of standard faza and purified 18 f - faza ( middle ), and only purified 18 f - faza ( right side of the plate ), air dried , and then developed by etoac . the rf of standard faza was determined by a uv absorption while the rf of the radioactive 18 f - faza was checked using ar 2000 bioscan tlc scanner . the rf of both standard faza and corresponding radioactive product appeared at same distance (± 0 . 05 ). the radiochemical purity of 18 f - faza always ranged & gt ; 95 %. three new precursors , diacetyl aza nosylate , 3 , dipivaloyl aza nosylate , 3a , and dipivaloyl aza tosylate , 8 , were designed in the class of compounds described in this invention to overcome the formation of secondary products during the radiofluorination that is encountered during the radiofluorination with aza tosylate . thermal deacetylation in nucleosides is a common phenomenon when the reactions are performed at elevated temperature (& gt ; 70 ° c .) ( 29 ). it leads to poor fluorination not only due to the formation of intramolecular oxirane rings to give 2 ′, 3 ′- anhydro aza tosylate and 2 ′, 5 ′- anhydro aza but also leads to the intramolecular hydrogen bond between neighboring tosyl moiety and deacetylated oh function . in addition , the carbons at − 2 ′ and − 3 ′ positions in arabinofuranose nucleus and the nitro group at c - 2 position in the 2 - nitroimidazole nucleus , being nucleophilic centre , are also prone to the attack by the fluoride leading to the possibility of formation of several fluorine substituted product ( 30 ). indeed , it was observed that additional radiofluorinated species are formed when 18 faza is synthesized from the aza tosylate . therefore , the radiofluorination profiles of two new faza precursors was explored , aza nosylate that might have a faster substitution rate due to more pronounced nucleophilic properties in comparison to the tolyl group , and pivaloyl aza tosylate which is thermally more stable and would therefore minimize the formation of oxirane related secondary products and , thus , provide a superior labeling quality of the mixture and the radiochemical yield . description of diacetyl aza nosylate , 3 , synthesis by methods a , b and c and dipivaloyl aza nosylate , 3a , by methods a and b and dipivaloyl aza tosylate , 8 , by methods a and c trimethylacetyl ( pivaloyl ) ethers provide similar electronic atmosphere to the molecule as do the acetyl groups ( 32 ), and are also reported to be more stable at higher temperatures ( 33 ). the development of 5 ′- o - tosylated / nosylated precursors with trimethylacetyl protective group at 2 ′- and 3 ′- oh groups would be an adequate replacement of the current faza ( and iaza ) precursor , tosyl aza , since it will also not alter the basics of the manufacturing process , which requires an alkaline hydrolysis of radiofluorinated product . the synthesis of 2 ′, 3 ′- di - o - trimethylacetyl - 5 ′- o - toluenesulfonyl aza , 8 , and 2 ′, 3 ′- di - o - trimethylacetyl - 5 ′- o -( 4 - nitrobenzene ) sulfonyl aza , 3a , started from aza , 1 , ( 34 ) which was selectively tosylated / nosylated , respectively , at 5 ′- oh group in anhydrous pyridine at 22 ° c . this tosylated , 7 , / nosylated , 7a , intermediate was treated with a solution of trimethylacetyl chloride in anhydrous pyridine at − 5 ° c . for 24 h to afford 8 ( 62 % yield ) and 3a ( 65 % yield ), respectively ( scheme 2 ). novel faza and iaza precursors 3 and 8 were radiolabeled according to the methods described in scheme 3 . radiofluorination of the precursors was performed using conditions that have been previously been shown to be compatible with commercially available automated synthesizers , such as the ge tracerlab , that are used in the generation of pet radiotracers for diagnostic and therapeutic applications ( 28 ). the labeling for these precursors was attempted at the temperatures ranging between 90 - 105 ° c . since the optimized yield for 18 f - faza from its diacetyl aza tosylate precursor is reported best at 100 ° c . ( 28 ). the experimental data are provided in table 1 . the skilled worked will appreciate that alternate methods of fluorination may used . the tlc chromatograms of unpurified post - labeling reaction mixtures from the precursors 3 and 8 ( fig2 a , b ) were acquired and their rfs were compared with standard faza ( co - spotting ) to analyze the radiofluorination yield of 18 f - faza from new precursors . it can be seen that both nosylate ( precursor 3 , fig2 b , reaction 13 , table 1 ) and pivaloyl tosylate ( precursors 8 , fig2 a , reaction 8 , table 1 ) offered much better radiochemical yields and cleaner chemical and radiochemical profiles for the reaction mixtures from these precursors in comparison to the current diacetyl aza - tosylate precursor ( commercially available ) that may offer a cartridge - based purification of the [ 18 f ] faza . using diacetyl aza nosylate 3 , the rcys for 18 f - faza were superior ( up to 80 %, uncorrected , fig2 b , reaction 13 ) in comparison to the corresponding pivaloyl precursor 8 ( fig2 a reaction 10 ). it was also observed that the radiochemical yields from the dipivaloyl aza tosylate precursor 8 did not alter too much ( except reactions 4 and 9 ) with the variation in the reaction temperature however the nosylate precursor 3 was affected by small changes (± 5 ° c .). fig2 depicts examples of tlc radiochromatography of the unpurified radiofluorinated reaction mixtures from a ) di - o - acetyl aza nosylate ( 95 ° c ., 10 min in dmso , ˜ 80 % of f - 18 faza is present , lot # fans0708 ) and ; b ) the purified 18 f - faza . the hplc - radiochromatography - based profile of the reaction mixtures from the novel precursors 3 ( fig3 a ) and 8 ( fig3 b ) reveal that the formation of secondary products , pre - and post - faza elution ( at retention times 15 - 28 . 5 min ), is minimal in comparison to when radiofluorination is attempted from diacts aza ( fig3 c ). synthesis of [ 18 f ] faza from its current precursor aza tosylate leads to additional recovery losses since several secondary products are formed near faza region that minimize its collection ( fig3 c ). additional radiofluorinated products are also seen in significant quantity from the reaction mixture of diacts aza at late ( after faza is eluted ) retention times (˜ 40 and ˜ 54 min ) with a slow elution pattern . this has been minimized in case of 18 f - faza reaction mixture obtained from 3 and 8 which improves both radiochemical yields , reduces the purification complicacy that is faced due to the formation of side products in currently used labeling procedure , and enables a simpler and facilitated recovery of pure 18 f - faza without any additional losses of radioactivity ( fig3 a , 3 b ). fig3 depicts hplc profile of impure faza reaction mixture from a ) dipivaloyl aza tosylate , 8 , and b ) diacetyl aza nosylate , 3 , indicating mainly unreacted 18 f - fluoride , 18 f - faza and demonstrating lesser side products in comparison to the mixture obtained from the tosylate precursor ( c ) that is being used currently for the clinical manufacturing uv signals in hplc chromatograms of the two mixtures ( fig3 a and b ) also demonstrate that the formation of radiochemical and chemical side products at retention times ˜ 14 - 28 . 5 min is much lesser in the reaction mixtures obtained from radiofluorination of 3 and 8 in comparison to the reaction mixture obtained from diacts aza ( fig3 c ). the stability of the precursor plays an important role in the quality of final product and the reaction mixture . its instability during the radiofluorination may lead to additional labeled species besides the desired product which would result in to significantly reduced yields of the desired product ( 18 f - faza ) and make its purification complicated , more so , when the labeled isotope has a short half life . the labeling of 18 f - faza using 5 ′- o - ts - 2 ′, 3 ′- diacetyl aza led to several additional labeled species , most likely , due to the reaction of fluoride with newly generated tosylates that are formed due to thermal deacetylation of the original tosylate precursor . the possibility of the formation of a c - 2 fluoro - aza product that may happen due to the nucleophilic displacement of c - 2 - nitroimidazole group in the diacetyl tosyl aza can also not be ruled out . although not identified , but the chromatogram of aza tosylate reaction mixture ( fig3 c ) demonstrates other radiolabeled species . this process is not observed with dipivaloyl aza tosylate since thermal deblocking is not reported with pivaloyl substituted precursors at this temperature . as a result , side products &# 39 ; formation is minimal when dipivaloyl tosyl aza is used as a precursor and leads to a less complicated hplc purification of 18 f - faza . pivaloyl - based aza tosylate and nosylate appear to be the better precursors among this class of the precursors for 18 f - faza labeling due to minimal side products formation . these precursors , and the reagents and conditions used to convert them to radiolabeled faza , are compatible for inclusion in kits that are used in commercial automated synthesizer units , such as the ge tracerlab , which are used to generate pet radiotracers for diagnostic and therapeutic applications . this invention demonstrates its application and potential in the development of other labeled compounds belonging to this class of compounds and related molecules as described in the current invention . . vaupel p . hypoxia and aggressive tumor phenotype : implications for therapy and prognosis . oncologist . 2008 ; 13 : 21 - 6 . . nordsmark m , m hoyer , j keller , o s nielsen , o m jensen , j . overgaard . the relationship between tumor oxygenation and cell proliferation in human soft tissue sarcomas . int j radiat oncol biol phys . 1996 ; 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