VINYL SUBSTITUTED CYCLIC PRODUCTS OF THE ENE-YNE REACTION

Abstract: This invention relates to a novel intermediate for use in solid phase chemistry, its preparation and methods of use of the intermediate.

Description: VINYL SUBSTTTUTED CYCLIC PRODUCTS OF THE ENE-YNE REACTION FIELD OF THE INVENTION This invention relates to a novel intermediate for use in solid phase chemistry, its preparation and methods of use of the intermediate. BACKGROUND OF THE INVENTION In the continuing search for new chemical moieties that can effectively modulate a variety of biological processes, the standard method for conducting a search is to screen a variety of pre-existing chemical moieties, for example, naturally occurring compounds or compounds which exist in synthetic libraries or databanks. The biological activity of the pre-existing chemical moieties is determined by applying the moieties to an assay which has been designed to test a particular property of the chemical moiety being screened, for example, a receptor binding assay which tests the ability of the moiety to bind to a particular receptor site. In an effort to reduce the time and expense involved in screening a large number of randomly chosen compounds for biological activity, several developments have been made to provide libraries of compounds for the discovery of lead compounds. The chemical generation of molecular diversity has become a major tool in the search for novel lead structures. Currently, the known methods for chemically generating large numbers of molecularly diverse compounds generally involve the use of solid phase synthesis, in particular to synthesize and identify peptides and peptide libraries. See, for example, Lebl et al., Int. J. Pept. Prot. Res., 41, p. 201 (1993) which discloses methodologies providing selectively cleavable linkers between peptide and resin such that a certain amount of peptide can be liberated from the resin and assayed in soluble form while some of the peptide still remains attached to the resin, where it can be sequenced; Lam et al., Nature, 354, p. 82 (19 1) and (WO 92/00091) which disclose a method of synthesis of linear peptides on a solid support such as polystyrene or polyacrylamide resin; Geysen et al., J. Immunol. Meth., 102, p. 259 (1987) which discloses the synthesis of peptides on derivatized polystyrene pins which are arranged on a block in such a way that they correspond to the arrangement of wells in a 96-well microtiter plate; and Houghten et al., Nature, 354, p. 84 (1991) and WO 92/09300 which disclose an approach to de novo determination of antibody or receptor binding sequences involving soluble peptide pools. The major drawback, aside from technical considerations, with all of these, methods for lead generation is the quality of the lead. Linear peptides historically have represented relatively poor leads for pharmaceutical design. In particular, there is no rational strategy for conversion of a linear peptide into a non-peptide lead. As noted above, one must resort to screening large databanks of compounds, with each compound being tested individually, in order to determine non-peptide leads for peptide receptors. Recently, there has been considerable interest in expanding the scope of polymer-supported chemistry for the preparation of increasingly more complex organic molecules, see, Marx et al., J. Am. Chem. Soc. 1997, 119, 6135-6167. This powerful technique has been used to rapidly produce large numbers of potentially biologically relevant compounds both in a combinatorial fashion and by multiple simultaneous syntheses, see, (a) An et al., J. Med. Chem. 1998, 41, 706-716; (b) Ostrem et al., Biochemistry 1998, 37, 1053-1059; and (c) Nicolaou et al., Angew. Chem. Int. Ed. Engl. 1997, 36, 2097-2103. We were interested in efficiently synthesizing a large number of novel compounds in a combinatorial fashion on solid support based on a structurally well-defined template. This led us to explore concise methods of synthesizing polycyclic ring systems, in particular, functionalized hexahydroisoindoline rings, as shown generically, in retrosynthetic fashion below in Scheme 1. Scheme 1 SUMMARY OF THE INVENTION This invention relates to a novel resin-bound compound of formula (I). Another aspect of the instant invention is in a method for making compounds using the resin-bound compound of formula (I) in solid phase synthesis. This method is applicable to making combinatorial libraries of compounds designed around a core molecular structure using known methods of solid phase combinatorial chemistry or multiple simultaneous synthesis ("parallel synthesis"). The compounds or libraries of compounds made using this technology may be tested in biologically assays designed to test for a particular physical characteristic potentially useful in drug therapy. DETAILED DESCRIPTION OF THE INVENTION The terms "resin," "solid support," "inert resin," polymeric resin", "polymeric resin support" or "POL" (used in the schemes) are used herein at all occurrences to mean a bead or other solid support such as beads, pellets, disks, capillaries, hollow fibers, needles, solid fibers, cellulose beads, pore-glass beads, silica gels, grafted co- poly beads, poly-acrylamide beads, latex beads, dimethylacrylamide beads optionally cross-linked with N,N'-bis-acryloyl ethylene diamine, glass particles coated with a hydrophobic polymer, etc., i.e., a material having a rigid or semi-rigid surface. The solid support is suitably made of, for example, cross linked polystyrene resin, polyethylene glycol-polystyrene resin, and any other substance which may be used as such and which would be known or obvious to one of ordinary skill in the art. The terms "resin-bound synthesis" and "solid phase synthesis" are used herein interchangeably to mean a series of chemical reactions used to prepare either a single molecule/compound or a library of molecularly diverse compounds, wherein the chemical reactions are performed on a compound of formula (I). It will be understood that additional synthetic chemistry may be performed on the resin-bound compound of formula (I), and that the end products, which will be resin-bound, may be cleaved from the resin using trifluoroacetic acid.. At the outset of this work, the level of substitution that could be tolerated on the ene-yne moiety was not well established and the ruthenium catalyzed ene-yne metathesis reaction had not been demonstrated on solid phase. 5 Ene-yne 3 should be available from an allyl amine, a carboxylic acid, and an appropriately functionalized alkyne. The feasibility of the chemistry was examined in solution (see Scheme 2 below) starting with 4-benzyloxybenzoic acid 4, which was chosen to mimic the linker found on Wang resin. Compounds 7a and 7b were prepared as shown in Scheme 2 using the known amines 5a and 5b (3-Amino-4-methylpent-l-ene (5b): Tamao, K.; Nakagawa, Y.; Ito, Y. J. Org. Chem. 1990, 55, 3438-3439) and the mesylates of the corresponding alkynols. Treatment of 7a and 7b with 3 mol% of RuCl 2 (=CHPh)(PCy 3 ) 2 (Kim, S.-H.; Bowden, N.; Grubbs, R.H. J. Am. Chem. Soc. 1994, 116, 10801-10802) under optimized conditions in degased, refluxing benzene, gave 8a and 8b in 90% and 89% isolated yields, respectively. These results confirmed that substitution at the terminus of the alkyne was not deleterious to the methathesis reaction and further established that sterically demanding substitution at the allylic position of the alkene was well tolerated (7b — > 8b). Next, we examined the Diels- Alder cycloaddition reaction to form the hexahydroisoindole ring system. The reaction conditions had to be compatible with our choice of acid labile solid support and therefore, we started with the thermally catalyzed reaction in refluxing toluene. Under these conditions diene 8b was condensed with maleimide to give the cycloadduct rac-9 in good yield as a single diastereomer. The results from Η NMR n.O.e. experiments are consistent with the relative stereochemistry shown in Scheme 2. The solution phase work showed that the reactions were either high yielding, or proceeded with moderate conversion and a very clean reaction profile, i.e. they gave only desired product and unreacted starting materials. We anticipated that the latter reactions could be driven to completion on solid phase by the use of excess reagents and/or multiple reaction cycles. Scheme 2 5a: R 2 = H 6a: R 2 = H 5b: R 2 = i-Pr 6b: R 2 = i-Pr 7a: R 2 = H, R 3 = H 7b: R 2 = i-Pr, R 3 = CH 3 8a: R 2 = H, R 3 = H 8b: R 2 = i-Pr, R 3 = CH 3 rac-9 (a) EDC, HOBt H 2 O, Et 3 N, DMF, RT, 18h (6a: 85%; 6b: 82%); (b) i - NaH, DMF, RT, 30 min, ii - R 2 CH,C≡CCH,OMs, RT, 5h (7a: 71%; 7b: 48% {recovered 6b; 41%}); (c) RuCl 2 (=CHPh)(PCy 3 ) 2 3 mol%, benzene, reflux, 18h (8a: 90%; 8b: 96%); (d) maleimide, toluene, reflux, 18h (30% {recovered 8b: 52%}). The solid phase chemistry was initiated by reacting the sodium anion of the allyl 4-hydroxybenzoate with chloro-Wang resin (Chloro-Wang resin was prepared from commercially available Wang resin (Polymer Labs; Lot No. WangOOδ; 250- 300 μM mesh; 1.7 meq/g loading) according to Raju, B.; Kogan, T.P. Tetrahedron Lett. 1997, 38, 4965-4968) in DMF to give 10. All of the reactions were characterized on solid phase using magic angle spinning Η NMR (MAS NMR). (The identity and purity of the products were further established by cleaving an aliquot of the resin-bound material with 5% H 2 O in TFA. In all cases, the desired resin-cleaved material was identified by mass spectroscopy and Η NMR analysis. The material was also >98% pure by reverse phase HPLC analysis.) The corresponding reaction of allyl 4-hydroxybenzoate with Wang resin under Mitsunobu reaction conditions (Hamper, B.C.; Dukesherer, D.R.; South, M.S. Tetrahedron Lett. 1996, 37, 3671-3674) was less successful, giving resin-bound material that was always contaminated with 5-10% resin-bound diethyl hydrazinedicarboxylate. (Apparently, the diethyl hydrazinedicarboxylate by-product of the Mitsunobu reaction effectively competed with the phenol as an alkylating agent for the resin. The side reaction could be suppressed by using a large excess of the allyl 4-hydroxybenzoate.) The allyl ester of 10 was removed using 20 mol% Pd(PPh 3 ) 4 in the presence of N-methyl aniline to give 11. (Seitz, O.; Kunz, H. Angew. Chem. 1995, 107, 901-904.) We initially loaded methyl 4-hydroxybenzoate onto the resin but were unable to successfully hydrqlyze the methyl ester under a variety of basic and nucleophilic conditions. Reaction of 11 with allyl amine or 3- amino-4-methyl-l-ρentene proceeded smoothly to give 12a or 12b as shown. Compounds 12a or 12b were treated with a 10- fold excess of lithium tert-butoxide to give the corresponding lithium amide. After draining away the excess lithium tert-butoxide, the resin-bound anion was reacted with a five-fold excess of 2-butynyl methanesulfonate in DMSO to give the desired products 13a and 13b, together with some unreacted starting material. This mixture was subjected to one more cycle of lithium tert-butoxide and 2-butynyl methanesulfonate to convert the remaining 12a or 12b to the corresponding products 13a and 13b. Other soluble strong bases, such as lithium, sodium, or potassium bis(trimethylsilyl)amide could not be used, as 13a and 13b were not stable to these conditions, and therefore the reaction could not be driven to completion through the use of multiple reaction cycles. Treatment of 13a and 13b with 5 mol% of RuCl 2 (=CHPh)(PCy 3 ) 2 in degased, gently refluxing benzene for 18h gave 14a and 14b. These results demonstrate that Wang resin and our choice of R 2 and R 3 do not have a detrimental effect on the efficiency of the metathesis reaction. Treatment of 14a and 14b with maleimide in refluxing toluene gave the resin-bound cycloadducts 15a and 15b as single diastereomers. The relative stereochemistry of 15a and 15b is as depicted in Scheme 3 and is consistent with nuclear Overhauser effects in the Η NMR spectrum of the material cleaved from resin. These results are similar to those obtained from the corresponding solution phase reaction, indicating that the resin did not influence the stereochemical outcome of the Diels-Alder cycloaddition reaction. This reaction sequence was used in a "split and mix" fashion to prepare a 10 x 4 x 5 x 16 membered isoindoline combinatorial library. (The R 1 component consisted of aryl or arylalkyl groups optionally substituted with halogen, alkyl and alkoxy groups. The R 2 component consisted of hydrogen, alkyl or arylalkyl groups. The R 3 component consisted of hydrogen or alkyl groups. The dienophiles included cyclic, cis and trans disubstituted olefins containing at least one electron withdrawing group and alkynes containing at least one electron withdrawing group) Scheme 3 10 11 12a: R 2 = H 13a: R 2 = H, R 3 = CH 3 12b: R 2 = i-Pr 13b: R 2 = i-Pr, R 3 = CH 3 (a) (Ph 3 P) 4 Pd, 10% PhNHCH, in 1: 1 DMSO/DMF, 55 °C, 18h; (b) EDC, HOBt H 2 O, Et 3 N, DMF, RT, 18h; (c) i - t-BuOLi, THF, RT, 1.5h, ii - R 2 CH 2 C≡CCH ; OMs, DMSO, 5h; (d) RuCl 2 (=CHPh)(PCy 3 ) 2 5 mol%, benzene, 75 °C, 18h; (e) maleimide, toluene, 105 °C, 18h. We selected 24 beads at random from each of the final 16 sublibraries and subjected them individually to 5% H2O in TFA followed by analyzing the resin- cleaved material by LC-MS. This revealed that, for 14 out of the 16 sublibraries, >70% of the beads examined contained identifiable material that was >70% pure by LC-MS analysis. Additionally, the LC-MS analyses of beads from 7 of the sublibraries revealed that there were 2 components present, comprising >70% of the material, with identical masses. This is consistent with the formation of diastereomeric Diels- Alders cycloaddition adducts. The LC-MS analysis of the beads from the remaining 2 out of the 16 sublibraries (those derived from the attempted Diels- Alder cycloaddition reactions with p-toluenesulfonyl cyanide and crotononitrile) gave no identifiable products. Alternatively, the reaction sequence can be used in conjunction with the IRORI Accu-Tag™ system to provide a tagging method to identify the specific sequence experienced by any given bead. In conclusion, we have demonstrated for the first time on solid support, a successful intra-molecular ruthenium-mediated ene-yne metathesis reaction to form a diene which was subsequently used in a Diels-Alder cycloadditon reaction. This invention relates to compounds of formula (I): Formula I wherein: X is N; and Y is R-CO, R-SO2, R-PO2, wherein R is 4-hydroxyphenyl, 4-hydroxy-3- methoxyphenyl, 3,5-dimethyl-4-hydroxyphenyl, 3-chloro-4-hydroxyphenyl, 3- hydroxy-4-methoxyphenyl, 3-hydroxyphenyl, 3-hydroxy-4-methylphenyl, 6- hydroxynapthyl, 4-hydroxyphenylmethyl, 4-hydroxyphenylethyl, can be prepared according to the teaching in copending patent application, Attorney Docket No. P50832P, USSN 60/098,532, filed August 31, 1998. See specifically, Schemes 1 and 2, and Examples 1 through 5. Scheme 4 a) Ph 3 P, diethylazadicarboxylate; b) Cp 2 Ti(Cl)CH 2 (Al(CH 3 ) 2 ; c) toluene, reflux; d) i - LiN(TMS) 2 , ii - MsOCH 2 C≡CCH 3 ; e) RuCl 2 (=CHPh)(PCy 3 ) 2 , benzene, reflux. Compounds of Formula (I), wherein X is C, Y = R-CO can be prepared as shown in Scheme 4. The substituent Y, is attached to the resin as previously described. The acid is coupled to the allylic alcohol containing the R 1 substituent using conventional methods, such as, triphenylphosphine and diethylazadicarboxylate giving the ester 3-Scheme 4. The ester is reacted with the Tebbe reagent giving the vinyl ether 4-Scheme 4 which is then heated in toluene at reflux to effect the Claisen rearrangement giving 5-Scheme 4. The enolate of 5-Scheme 4 is prepared using a strong base, such as, lithium bis(trimethylsilyl)amide and is treated with a suitable l-mesyl-2-alkynyl moiety containing the R 2 substituent. A 1-halo-, or l-tosyl-2-alkynyl moiety containing the R 2 substituent can also be employed. An intramolecular ene-yne metathesis reaction using a suitable catalyst, such as, bis(tricyclohexylphosphine)benzylidene ruthenium dichloride furnishes the diene " U Scheme 4. Scheme 5 a) t-BuOLi; b) i - n-Bu 4 NF, ii - t-BuOLi, iii - MsOCH 2 C≡CCH 2 CH 3 ; c) RuCl 2 (=CHPh)(PCy 3 ) 2 , benzene, reflux. Compounds of Formula (I), wherein X is N, Y is Ar can be prepared as shown in Scheme 5. A suitably protected substituent Y, using, for example, the trimethylsilylethoxy-carbonyl protecting group, is attached to the solid support as previously described. The carbamate 1 -Scheme 5 is deprotonated with a soluble base, such as, lithium tert-butoxide and is reacted with an allyl bromide containing the R 1 substituent, ' such as, 3-bromo-l-butene giving the subtituted carbamate 3; Scheme 5. The protecting group is removed by conventional methods, such as, tetra-n-butylammonium fluoride. The resulting amine is deprotonated with a soluble base, such as, lithium tert-butoxide and reacted with a l-methanesulfonyl-2-alkyne which contains the R 2 group. A 1-halo-, or l-tosyl-2-alkynyl moiety containing the R 2 substituent can also be employed. An intramolecular ene-yne metathesis reaction using a suitable catalyst, such as, bis(tricyclohexylphosphine)benzylidene ruthenium dichloride furnishes the diene 5-Scheme 5. Scheme 6 a) THF, -78 °C; b) i - PPh,, CBr 4 , ii - CH 2 =CH-CH(Li)CH 3 ; c) RuCl 2 (=CHPh)(PCy 3 ) 2 , benzene, reflux. Compounds of Formula (I), wherein X is C, and Y is R-CO can be prepared as shown in Scheme 6. A suitable epoxide containing the substituent Y, such as, 4- hydroxystyrene oxide is attached to the solid support as previously described giving 1 -Scheme 6. The epoxide is opened with a lithiated alkyne containing the R 3 substituent, such as, 1-lithiopropyne givign the alcohol 3-Scheme 6. The hydroxyl group of 3-Scheme 6 is converted to a leaving group using conventional methods, such as, triphenyl phosphine and carbon tetrabromide and is then reacted with a 3- lithio-1-propene containing the R 2 substituent giving 4-Scheme 6. An intramolecular ene-yne metathesis reaction using a suitable catalyst, such as, bis(tricyclohexylphosphine)benzylidene ruthenium dichloride furnishes the diene 5; Scheme 6. Based upon the disclosure herein, it will be clear to one of ordinary skill in the art that there are many possible synthetic approaches to creating the libraries of this invention. For example the libraries may be prepared using the split and mix technique or parallel synthesis techniques. The libraries generated from either of the the synthetic methods are molecularly diverse and are prepared simultaneously. It will be obvious to one of skill in the art that the steps of optionally dividing and recombining the resin-bound aryl silane intermediate into portions are for purposes of varying the derivatization on the resin-bound nucleophiles which are generated by the combinatorial synthesis. Of course, it will be obvious to the skilled artisan that the resin-bound nucleophile intermediates may be divided into portions at any point during the synthetic sequence. The portions may be recombined at any point during the sequence or, further iterations may be applied if more derivatization is required. Therefore, it will be obvious to the skilled artisan that the steps of dividing the portions, performing additional synthetic chemistry and recombining to the portions, may each be carried out more than once, depending upon the type of diversity required for the library of end-product compounds being prepared. According to this invention, after the additional synthetic chemistry has been performed on the resin-bound aryl silane intermediate so that a library of moiecularly diverse compounds has been prepared, the compounds can be separated and characterized by conventional analytical techniques known to the skilled artisan, for example infrared spectrometry or mass spectrometry. The compounds may be characterized while remaining resin-bound or they can be cleaved from the resin using the conditions described above, and then analyzed. In addition, a partial array of compound members of the library may be cleaved from the resin, characterized and analyzed, while leaving a partial array of the compound members of the library bound to the resin. The above description fully discloses the invention including preferred embodiments thereof. Modifications and improvements of the embodiments specifically disclosed herein are within the scope of the following claims. Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. Therefore any examples are to be construed as merely illustrative and not a limitation on the scope of the present invention in any way. The embodiments of the invention in which an exclusive property or privilege is claimed, are defined as follows. I I

Claims: What is claimed is: 1. A resin-bound compound of formula (I) Formula I wherein: X is N, or CH; Y is Ar, R-CO, R-SO2, R-PO2; POL is a polymer resin; R is 4-hydroxyphenyl, 4-hydroxy-3-methoxyphenyl, 3,5-dimethyl-4-hydroxyphenyl, 3-chloro-4-hydroxyphenyl, 3-hydroxy-4-methoxyphenyl, 3-hydroxyphenyl, 3- hydroxy-4-methylphenyl, 6-hydroxynapthyl, 4-hydroxyphenylmethyl, 4- hydroxyphenylethyl; RI is hydrogen, lower alkyl (branched or straight chain), halogen,or (CH2)θ-6" Prι ; R 2 is CO 2 R, hydrogen, CH2-R, or Si(CH3)3; m is 1 to 3; and n is 1-3; provided that n plus m is 2 to 4, and provided that when X is N, R s halogen only if n is 2.

Inventors: HEERDING DIRK A, HEERDING, DIRK, A.
Applicants: HEERDING DIRK A, SMITHKLINE BEECHAM CORP, HEERDING, DIRK, A., SMITHKLINE BEECHAM CORPORATION
Application year: 1999
Main classification: C07F7
IPC codes: C07B61, C07C39, C07C49, C07D207, C07D487, C08F8