Decoding Products of Diversity Pathways from Stock Solutions Derived from Single Polymeric Macrobeads

Efficient phenotypic and proteomic screening of small molecules derived from diversity-oriented organic syntheses[1] requires a library realization platform[2] that 1) produces a sufficient quantity of compound per bead to perform many hundreds of assays[3] and 2) supports reliable compound structure identification. To facilitate the latter, solid-phase library-encoding strategies[4] have been developed that allow the identity of the compounds to be inferred postsynthesis directly from individual beads.[5] We recently adapted the chemical-encoding strategy introduced by Still and co-workers[6] to a high-capacity (1.4 mequiv gy1 100 nmol/bead), 500 ± 600 mm polystyrene (PS) solid support (Scheme 1),[3] a key element of a aone-bead, one-stock-solutiono technology platform.[7] We have now discovered that the stock solutions of compounds cleaved from individual beads contain sufficient tags to allow the structures of their corresponding small molecules to be inferred reliably. Two methods used for the decoding of the library of 4320 dihydropyrancarboxamides reported in the preceding Communication are described.[8] The encoding method features structurally related chloroaromatic diazoketone atagso,[6b] which are introduced through an acylcarbene insertion into the phenyl rings of PS catalyzed by [Rh2(O2CCPh3)4] (1) to yield cycloheptatrienes (Scheme 1).[9] To decode a library compound, the tags are cleaved oxidatively from the solid support with ceric ammonium nitrate (CAN) to yield free alcohols,[10] which are then silylated (with N,O-bis-(trimethylsilyl)acetimide, BSA) and injected directly onto a gas chromatograph equipped with electron-capture detection (GC/ECD) for analysis (each tag trimethylsilyl ether has a unique GC retention time). For lowloaded solid support ( 100 pmol/bead) it has been postulated that the carbene inserts predominantly into the support due to 1998, 37, 3372 ± 3375; c) J. Thorhauge, M. Johannsen, K. A. Jurgensen, Angew. Chem. 1998, 110, 2543 ± 2546; Angew. Chem. Int. Ed. 1998, 37, 2404 ± 2406. [9] S. Leconte, G. Dujardin, E. Brown, Eur. J. Org. Chem. 2000, 639 ± 643; for a related heterocycloaddition on solid support, see: L. F. Tietze, T. Hippe, A. Steinmetz, Synlett 1996, 1043 ± 1044; for a report of an asymmetric cycloaddition with external control on a solid support, see ref. [5d]. [10] a) J. A. Tallarico, K. M. Depew, H. E. Pelish, N. J. Westwood, C. W. Lindsley, M. D. Shair, S. L. Schreiber, M. A. Foley, J. Comb. Chem. 2001, 3, 312 ± 318; b) H. E. Blackwell, L. PeÂrez, R. A. Stavenger, J. A. Tallarico, E. Cope-Eatough, M. A. Foley, S. L. Schreiber, Chem. Biol. , submitted; c) P. A. Clemons, A. N. Koehler, B. K. Wagner, T. G. Sprigings, D. R. Spring, R. W. King, S. L. Schreiber, M. A. Foley, Chem. Biol. , submitted. [11] a) M. H. J. Ohlmeyer, R. N. Swanson, L. W. Dillard, J. C. Reader, G. Asouline, R. Kobayashi, M. Wigler, W. C. Still, Proc. Natl. Acad. Sci. USA 1993, 90, 10922 ± 10 926; b) H. P. Nestler, P. A. Bartlett, W. C. Still, J. Org. Chem. 1994, 59, 4723 ± 4724. [12] H. E. Blackwell, L. PeÂrez, S. L. Schreiber, Angew. Chem. 2001, 113, 3529 ± 3533; Angew. Chem. Int. Ed. 2001, 40, 3421 ± 3425. [13] A fully automated procedure for deriving and arraying stock solutions from the dihydropyrancarboxamide-containing macrobeads described herein has been developed and will be reported elsewhere; ref. [10c]. [14] After surveying several loading/ligand/metal/solvent combinations, 20 mol % of 1 in THF was found to provide the best combination of kinetics and selectivity. [15] The configurations of the cycloadducts were assigned by analogy. See refs. [8a, c]. [16] We have ruled out isomerization of the alkenyl ether and epimerization of the acetal center as reasons for the lower selectivity. [17] The details of this procedure and the relationship between the 108 cleaved compounds and their associated electrophoretic tags are reported in ref. [12]. [18] For 25 of the 108 samples, the molecular ion observed upon ionization corresponded to a fragment of the compound. [19] To the best of our knowledge, this is the first report of the use of a substoichiometric amount of chiral controller to perform a carbon ± carbon bond forming reaction on solid phase. [20] a) G. MacBeath, A. N. Koehler, S. L. Schreiber, J. Am. Chem. Soc. 1999, 121, 7967 ± 7968; b) P. J. Hergenrother, K. M. Depew, S. L. Schreiber, J. Am. Chem. Soc. 2000, 122, 7849 ± 7850. [21] A. N. Koehler, S. L. Schreiber, unpublished results. [22] Supporting Information available: Full experimental details and spectral data for building block and library syntheses.