PROCESSES AND INTERMEDIATES FOR PREPARING MACROCYCLES

Abstract: Novel processes for the preparation of lactam- and lactone-containing macrocycles are provided. In preferred embodiments, rapamycin and demethoxyrapamycin are prepared by a convergent synthesis regime. Intermediates useful in the synthetic processes are also provided.

Description: PROCESSES AND INTERMEDIATES FOR PREPARING MACROCYCLES GOVERNMENT SUPPORT Certain of the inventors were supported by National Institutes of Health Grant GM29026. FIELD OF THE INVENTION This invention relates to methods for the preparation of lactam- and lactone-containing macrocycles such as rapamycin and demethoxyrapamycin, and to intermediates useful in their preparation. BACKGROUND OF THE INVENTION Rapamycin and demethoxyrapamycin are two members of a growing class of macrolide natural products possessing marked immunosuppressive properties . RtT-rer tly, several groups have focused on the preparation of both modest and advanced fragments of the polyketide skeletc::, culminating in three total syntheses of rapamycin. In addition, several groups have prepared semi-synthetic analogs of rapamycin to improve upon its impressive therapeutic profile as well as to gain insight into the as-ye -unresolved mechanism of action. To date, four research groups have reported the discovery and isolation of a 220 kDa protein which is thought to be the direct intracellular target cf the rapamycin-FKΞ? complex. This protein shares structural homology with a number of known lipid kinases although its specific role in signal transduction and immunosuppression remains unclear. It ha however, been established that rapamycin interferes with a Ca 2 independent signaling pathway emanating frcm the I -2 recepto thus prohibiting the progression of activated T cells frcm t Gl to the S phase of the cell cycle, perhaps via indire inhibition of a cyclin dependent kinase specifically requir for this transition. There is a need for improved synthetic methods for t preparation of rapamycins. This invention is directed to th important end. OBJECTS OF THE INVENTION It is one object of the present invention to provid lactam- and/or lactone-containing macrocycles; It is a further object to provide processes for th preparation of rapamycin, demethoxyrapamycin, and C-2 epirapamycin. It is another object of this invention to provid intermediates useful in the processes. SUMMARY OF THE INVENTION These and other objects are satisfied by the presen invention, which provides synthetic methods for the preparatio of macrocycles, and novel compounds useful in the syntheses. In certain embodiments, methods are provided for th Drenaration of a compound havincr formula (VI-I) Vll comprising the steps of: providing a first compound of formula IV: and contacting said compound with a compound c formula (VI) : VI for a time and under reaction conditions effective to form said compound of formula VII; wherein: R j , R « , and R 9 are, independently, hydrogen or a hydroxyl protecting group; R, is alkyl having one to about six carbons; R 7 is hydrogen or alkoxy having one to about six carbons; R 10 is H, OK, or alkoxy having one to about six carbons; R 21 is alkyl having one to about six carbons; M is a metal atom; and x is halogen. In preferred embodiments R 7 is H or ethoxy, and is Sn. Preferably the hydroxyl protecting groups are selected from the group consisting cf TIF≤, FM30, TΞSO and TB£ . More preferably, R, is TIPS; R 3 is K; R 4 is TES; and R, is TES. Preferred embodiments further comprise treating said compound cf formula VII for a time and under reaction conditions effective to form a compound cf formula XV: ~xV ~ Preferably, the protecting groups are then removed. Also provided is a method for the preparation of a compound of formula IV: comprising the steps of: providing a compound of formula II treating said compound of formula II for a time and under conditions effective to form a terminal acetylene of formula III: and treating said terminal acetylene for a time and under conditions effective to form said compound of formula IV. In some preferred embodiments said compound cf formula II is formed bv the reaction of an eooxide of formula V: T and a reaσent cf formula XVI In other preferred embodiments said compound of formula II is formed by the reaction of an aldehyde of formula XIII: SU and a reaσent of formula XVI fflά d X V I Also provided is a method for the preparation of a divinyl halide of formula VI: comprising the steps of: providing an orthoester cf formula IX; treating said orthoester for a time and unde: conditions effective to form an aldehyde cf formula X; contacting said aldehyde with 2-carboxy-N- acetoylpiperidine for a time and under conditions effective to form a compound of formula XII; and treating said compound cf formula X1 Z for a time and under conditions effective to form said civinyl halide of formula VI. Also provided according tc the invention are novel intermediates, useful in the methods of the invention, having formula I: wne em: R : , R 3 and R 4 are independently K or a hydroxyl protecting group; R : is alkyl having frcm one to six carbons; R 7 is H or alkoxy; R :3 is carbonyl group or protected derivative thereof; R : . has the formula -CH(OCH 3 ) 2 , -CsC-R 12 or cis-CH=CH- M(nC 4 H 9 ) 3 ; wherein: R 12 is H or trimethylsilyl; and M is a metal atom. In certain preferred embodiments R 7 is K, and in other preferred embodiments R 7 is methoxy. Preferably, R ι: has the formula -CK(OCK 3 ) 2 , -CsC-R,, or cis-CH=CH-M(nC 4 H 9 ) 3 ; and M is Sn. The compound of claim 6 wherein R is K. In certain preferred embodiments R ;ι is -CK(OCK 3 ) 2 or -CsC-R 12 , and said protected derivative of said carbonyl group of said group R 13 is a l,3-dithiane. Preferably, R 2 is methyl; and said hydroxyl protecting groups are selected from the group consisting of TIPS, PMBO, TΞS and TBS. In particularly preferred embodiments R : is TIPS, R 3 is PMB and R 4 is TBS. Also provided are compounds cf formula V: T wherein R : , R 2 , R 3 and are as de f ined above . Compound are also provided having formula V] wner m: R 9 is H or a hydroxyl protecting group; R 13 is K, OH or alkoxy having one to about six carbon atoms,- and X is halogen, preferably iodine. In certain embodiments R β is K, and R 10 is methoxy. Also provided are compounds having formula VII: wnnerem R 2 , R 4 , R 7 , R 9 L3 ' R-, and M are as defined above BRIEF DESCRIPTION OF THE DRAWINGS The numerous objects and advantages of the present invention may be better understood by those skilled in the art by reference to the accompanying figures, in which: Figure 1 shows an overview cf a synthesis cf the invention as applied to rapamycin and demethoxyrapamycin. Figure 2 shows the preparation of compounds XV and VII from compounds IV and VI . Figure 3 shows the preparation of fragment IV from precursor compound II. Figure 4 shows exemplary synthetic routes for the derivation of compound II where R 7 is H or alkoxy. Figure 5 shows the preparation of compound VI from fragment D. Figure 6 shows the formation cf compound II in the synthesis of demethoxyrapamycin. Figure 7 shows the formation of compound II in the synthesis of rapamycin. Figure 8 shows the synthesis of compound VI (fragment DE) from fragment D. Figure 9 shews the completion of the synthetic routes to rapamycin and demethoxyrapamycin from compounds Ila and lib. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS It has been found in accordance with the invention that the synthesis of macrocycles such as rapamycin and/or derivatives can be achieved by highly convergent synthetic procedures wherein fully functionalized fragments corresponding to carbons 21-34 of the rapamycin skeleton are coupled with pinecolinate-tricarbonyl fragments corresponding to carbons 1- 20, each fragment being available from building blocks A through E as outlined in Figure 1. In preferred embodiments rapamycin or demethoxyrapamycin are prepared from compound VII, which is in turn prepared frcm precursor fragments IV and VI according to Figure 2. Preferably, compound IV is first coupled to compound VI by an intεrmolecular acylaticn tc form compound VIZ. A preferred condensation agent for the acylaticn is ethyl-3-( dimethyla ino) -propyl carbcdii ide • KCl {E-DAC-KCl} dimethylamino pyridine (DMA?) . Clcsure cf the ring in compou VII is preferably achieved by a pd (0) -catalyzed Stil coupling. A preferred reagent for the coupling is ( furyl,? ) jPdCl,, diiscpropylethyla ine (DIFΞA) i CMF/TKF. Aft ring closure, the protecting groups are preferably removed b any cf several reagents known in the art to be suitable, fo example tetrabutyla monium fluoride/acetic acid (TΞAF/AcOK followed by KF- yridine, pyridine in TKF. The methods of the present invention allow flexibilit in choice of substituents on the rapamycin skeleton. Fo example, R, can be varied to provide different rapamyci derivatives. In one preferred embodiment R 7 is hydrogen, an the resulting product is demethoxyrapamycin. Other simila substitutions may be made at other positions in the rapamyci skeleton, for example, at C-16. The preparation of fragment IV frcm common precursor compound II is shown in Figure 3. Compound II is first treated to unmask the aldehyde group by reaction with, for example, TsOK in acetone, and then subjected to Corey-Fuchs homolσgation to yield the terminal acetylene compound III. See, Corey, E.J. and Fuchs, P.L., Tetrahedron Let . 1972 13 , 3769. Compound III is, in turn, treated to remove the protecting group at C-34. In preferred embodiments the protecting group at C-34 is FM30 (p-methoxybenzyloxy) , which is preferably removed oxidatively by, for example, DDQ (2, 3-dichloro-5, 6-dicyano-l, 4- benzocuinone) in CH 2 C1 2 . This is followed by hydrolysis cf the dithiane group with, for example, Mel, CaC0 3 , and palladium(O) - mediated hydrostannylatio . See Zhang, H.X. et al . , " . Or_r. Cher, . 1990 55, 1857. Compound II derives from two separate synthetic routes depending upon the nature of R,. These synthetic routes are shewn in Figure 4. In the synthetic route leading, for example, to demethoxyrapamycin, fragment B from Figure 1 is coupled with the b tyilithiu derivative cf fragment A of Figure 1 tc produce precursor acetcnide VIII (fragment AS) . Fragments A and B can be prepared according to the procedure of Smith, A.E. et al., Te trahedron Le t ters 1994, 35 (25) , 4907-4910. Epcxide V is produced frcm compound VIII by standard techniques, such as, for example, unmasking with camphorsulfcnic acid/methanol (C≤A/MeOK) , tosylation, and epoxidaticn with K ; C0 3 /MeOK. Compound II (R 7 = K) is fcrmed frcm the coupling cf terminal epoxide V and compound XVI. Freferably, the coupling is performed at low temperature (i.e., -78°C) using an alkyllithiu reagent, for example t-EuLi, in an appropriate solvent such as, for example, 10 h (v/v) KMPA (hexamethylphosphoramice) /TKF. In the synthetic route leading to, for example, rapamycin, aldehyde XIII is first produced by coupling fragment A frcm Figure 1 with the lithium derivative of dithiane compound XVII. Fragment C from Figure 1, prepared according to the procedure of Smith, A.B. et al . , Te trahedron Letters 1994, 35 (28) , 4911-14 is metallated with t-butyllithium and added to aldehyde XIII, and the product is methylated to give compound II (R = OCK 3 ) . The preparation of compound VI is shown in Figure 5. Fragment D from Figure 1, prepared according to the procedure in Smith, A.E. et al. , Tetrahedron Le t ters 1994, 35 (28) , 4911-14, is hydrolyzed with, for example, AcOK/TKF, and silated with, for example, 2 equivalents cf TBSCl ( -butyldimethylsilyl chloride) , i idazole, DMF. The ester is reduced by, for example DIBAL (diisobutylaluminu hydride) reduction, and aldehyde species X is formed by subsequent oxidation, for example with DMSO and oxalyl chloride by the method of Swern. See, March, J., Advanced Organi c Chemis try Fourth Ed . Wiley & Sons New York, 1992 p. 1194. Compound X is then condensed with the dianion cf (L ) - N-acetylpipecolinic acid in the presence of a condensing agent such as, for example, lithium hexamethyldisilazide (LKMD≤) . The products are treated with diazcmethane followed by Des- Martin oxidation (5 equiv) to give the tricarbonyl species in accordance with the procedure developed by Golec, et al . See , Batchelor, M.J. et al . , Te trahedron Le t . , 1993, 34 , 167 ; Dees, D.B et al . , J. Org . Cher.. 1983 48 4155. Removal of the TSS group at C-14 yields the hemiketal compound XII, which is thϊ protected at the free hydroxyl groups by, for example, reaction with triethylsilyltrifluoro ethane s lfonate (TESOTf) . Compound VI (fragment DΞ) is then formed from compound XII by free radical hydrostannylaticn according to the procedure of icolaou, et al . , Syn thesis 1986, 453, using, for example Eu 3 SnK, 2,2' -azobisiscbutrylcnitrilε (AIB ) , tin-iodide exchange according to the procedure of Crisp, e t al . , Te trahedron Le tters 1992, 33 (32) , 4S49, and subsequent conversion of the ester to the carboxylic acid by, for example, LiI in pyridine. Compounds of the invention contain protecting groups. Protecting groups are known per se as chemical functional groups that can be selectively appended to and removed from functionalities, such as hydroxyl groups and carboxyl groups. These groups are present in a chemical compound to render such functionality inert to chemical reaction conditions to which the compound is exposed. Some representative protecting groups useful for protecting the for carbonyl functionality are 1,3-dithiane groups and dimethσxyacetal groups. Some representative protecting groups useful for protecting the for hydroxyl functionality are TIPS (triisopropylsilyl) , PMΞ (p- methoxybenzyl) , TBS (t-butyldimethylsilyl) , TES (triethylsilyl) and lower alkyl groups such as methyl. Other representative groups may be found in Greene, T.W. and Wuts, P.G.M., "Protecti ve Groups in Organic Synthesis " 2d. Ed., Wiley & Sons, ■ 1991. In preferred embodiments R_ is TIPS, R 3 is PM3, R. is TBS, and R, is TES. R 2 is preferably hydrogen or alkyl having from one tc about six carbons. Alkyl groups according to the invention include straight chain, branched, and cyclic hydrocarbons such as methyl, isopropyl, and cyclchexyl groups. Alkoxy groups are oxygen atoms having an alkyl group appended thereto. It will be recognized that a wide variety of compounds according to the invention can readily be prepared according to the methods of the invention. Those skilled in the art will appreciate that numerous changes and modifications may be made to the preferred embodiments of the invention and that such changes and modifications may be made without departing frcm the spirit cf the invention. It is therefore intended that the appended claims cover all equivalent variations as fall within the true spirit and scope of the invention.

Claims: WHAT IS CLAIMED IS: 1. A compound of formula (I) : wherein: R lf R 3 and R 4 are, independently, H or a hydroxyl protecting group; R 2 is alkyl having from one to about six carbons; R 7 is H or alkoxy having one to about six carbon- atoms; R x3 is carbonyl group or protected derivative thereof; R__ has the formula -CH(OCH 3 ) 2 , -C≡C-R 12 cr trans-CH=CK- M(R 21 ) 3 ; R 12 is H or trimethylsilyl; and R 21 is alkyl having one to about six carbon atoms; M is a metal atom. 2. The compound of claim 1 wherein R, is K. 3. The compound cf claim 1 wherein R 7 is methoxy. 4 . The compound of claim 1 wherein R : . has formula -CH(OCK ) 2 . 5. The compound of claim 1 wherein R :ι has formula - C≤C- R : - . 6. The compound of claim 1 wherein R :: has formula Crans-CK-CH- (nC 4 K 9 ) 3 . 7. The compound of claim 6 wherein M is Sn. 8. The compound of claim 6 wherein R 3 is K. 9. The compound of claim 4 or claim 5 wherein said protected derivative of said carbonyl group of said group R 1 is a 1,3-dithian . 1C . The compound of claim 1 wherein R 2 is methyl. 11. The compound of claim 1 wherein said hydroxyl protecting groups are selected from the group consisting cf TIPS, PMBO, TES and TBS. 12. The compound of claim 1 wherein R_ is TIPS, F. 3 is PMB and R 4 is TBS. 13. A compound of formula (V) : T wnerem: R x and R, are, independently, K or a hydroxyl protecting group; R 2 is alkyl having frcm one to about six carbons; and R 13 is carbonyl group cr protected derivative thereof. 14. A compound of formula (VI) : wherein: R 9 is H or a hydroxyl protecting group; R 10 is H, OK, or alkoxy having one to about six carbon atoms; and X is halogen. 15. The compound of claim 14 wherein R β is K, and R 10 is methoxy. 16. The compound of claim 14 wherein X is iodine. 17. A compound cf formula VII: VI wherein: R x , R 4 , and R 9 are, independently, hydrogen or a hydroxyl protecting group; R 7 is hydrogen or alkoxy having one to about six carbon atoms; R 13 is K, OK, or alkoxy having one to about six carbon atoms; R 21 is alkyl having one to about six carbon atoms; and X is haloσen. 16. A method for the preparation of a compound having formula VII comprising the steps of: providing a first compound of formula IV; and contacting said first compound with a second compound of formula VI for a time and under reaction conditions effective to form said compound of formula VII; wherein: R : , R 3 , R , R 9 and R 9 are, independently, hydrogen cr a hydroxyl protecting group; R, is alkyl having from one to abcut six carbons; R 7 is hydrogen cr alkoxy having one to about six carbon atoms; R 13 is a carbonyl group cr a protected derivative thereof; R 10 is H, OH, or alkoxy having one to about six carbon atoms; R 21 is alkyl having one to about six carbon atoms; and X is halogen. IS. The method of claim 18 wherein R 7 is K. 20. The method of claim 18 wherein R 7 is methoxy. 21. The method cf claim 13 wherein M is Sn . 22. The method of claim 18 wherein said hydroxyl protecting groups are selected from the group consisting of TIPS, PMBO, TESO and TBS. 23. The method of claim 18 wherein R : is TIPS; R 3 is K; R 4 is TES; and R 9 is TES. 24. The method of claim 18 further comprising treating said compound of formula VII for a time and under reaction conditions effective to form said a compound of formula XV. 25. The method of claim 24 further comprising the step cf removing said protecting groups. 25. A method for the preparation of a compound of formula IV comprising the steps of: providing a compound cf fcrmuia II; treating said compound cf formula II for a time and under conditions effective to form a terminal acetylene of formula III; and treating said terminal acetylene for a time and under conditions effective to form said compound cf formula IV. 27. The method of claim 26 wherein R 7 is K. 28. The method cf claim 26 wherein R 7 is methoxy. 29. The method of claim 27 wherein said compound of formula II is formed by the reaction cf an epoxide of formula V and a reagent of formula XVI. 30. The method of claim 28 wherein said compound of formula II is formed by the reaction of an aldehyde of formula XIII and a reagent of formula XVI. 31. A method for the preparation of a divinyl halide of formula VI comprising the steps of: providing an orthoester of formula IX; treating said orthoester for a time and under conditions effective to form an aldehyde of formula X; contacting said aldehyde with 2-carboxy-N-acetoylpiperidine for a time and under conditions effective to form a compound of formula XII; and treating said compound of formula XII for a time and under conditions effective to form said divinyl halide cf formula VI .

Inventors: CONDON STEPHEN M, LEAHY JAMES W, LEAZER JOHNNIE L JR, MALECZKA ROBERT E, MCCAULEY JOHN A, SMITH AMOS B III, CONDON, STEPHEN, M., LEAHY, JAMES, W., LEAZER, JOHNNIE, L., JR., MALECZKA, ROBERT, E., MCCAULEY, JOHN, A., SMITH, AMOS, B., III
Applicants: UNIV PENNSYLVANIA, THE TRUSTEES OF THE UNIVERSITY OF PENNSYLVANIA
Application year: 1995
Main classification: C07C35
IPC codes: C07C35, C07C49, C07D303, C07D405, C07F7