We present the development of new affinity probes for protein labeling based on an epoxide reactive group. Systematic screening revealed that an epoxide functionality possesses the special combination of stability and reactivity which renders it stable toward proteins in solution but reactive on the protein surface outside the active site (proximity-induced reactivity). Highly efficient and selective labeling of purified HCA II (human carbonic anhydrase II) was achieved. For instance, 2 equiv of epoxide probe 9 was sufficient for nearly quantitative labeling of HCA II (>90% yield, 20 h reaction time). MS analysis of the labeled protein revealed that 1 equiv of the probe was attached and that labeling occurred at a single residue (His 64) outside the active site. Importantly, epoxide probe 9 selectively labeled HCA II both in simple protein mixtures and in cellular extracts. In addition to the chemical insight and its relevance to many epoxide-containing natural products, this study generated a promising lead in the development of new affinity probes for protein labeling.

references therein. [lo] A linear relation between (l,/Dopl/DJ and A?,,,ax (where D,, and D, are optical and static dielectric constants) has been obtained with a slope of 6200cm.' and an intercept of 5800cm-' [ l l ] S.

YCl 3 , SmCl 3 , and LuCl 3 react with (tetramethylvinylcyclopentadienyl)lithium (1a), yielding (CH 2 dCHC 5 Me 4 ) 2 Ln(µ-Cl) 2 Li(Et 2 O) 2 (Ln ) Y (2a), Sm (2b), Lu (2c)). LuCl 3 and the analogous potassium salt 1b form oligomeric [(CH 2 dCHC 5 Me 4 ) 2 Lu(µ 3 -Cl) 2 K(THF)] n (3). Methylation of the yttrium complex 2a with MeLi gives (CH 2 dCHC 5 Me 4 ) 2 Y(µ-CH 3 ) 2 Li(THF) (4). Hydroboration of the complexes 2a-c with 9-BBN results in the formation of (C 8 H 14 BCH 2 -CH 2 C 5 Me 4 ) 2 Ln(µ-Cl) 2 Li(THF) 2 (Ln ) Y (5a), Sm (5b), Lu (5c)). The reaction of YCl 3 with 2 equiv of K[C 5 H 4 CHdC 6 H 10 ] (6) or K[C 5 H 4 CHdCMe 2 ] (10) affords the dimeric complexes [(C 6 H 10 dCHC 5 H 4 ) 2 Y(µ-Cl)] 2 (7) and [(Me 2 CdCHC 5 H 4 ) 2 Y(µ-Cl)] 2 (11), whereas SmCl 3 reacts with 2 equiv of 6 or 10, yielding the tris(cyclopentadienyl) derivatives (C 6 H 10 dCHC 5 H 4 ) 3 -Sm(THF) ( 9) and (Me 2 CdCHC 5 H 4 ) 3 Sm(THF) (13), respectively. Methylation of 7 with MeLi yields unstable [(C 6 H 10 dCHC 5 H 4 ) 2 Y(µ-CH 3 )] 2 (7a). SmI 2 and 6 react with formation of (C 6 H 10 d CHC 5 H 4 ) 2 Sm(THF) 2 (8). Hydrolysis during crystallization of 11 caused by some water in the solvent leads to decomposition, forming the oxygen-bridged complex [(Me 2 CdCHC 5 H 4 ) 2 Y-(Et 2 O)] 2 (µ-O) (12). The ansa-lanthanidocene chloride [H 2 CdC(CH 2 C 5 H 4 ) 2 ]LuCl(THF) (15) was prepared from LuCl 3 and the new ligand K 2 [H 2 CdC(CH 2 C 5 H 4 ) 2 ] ( 14). The structures of 2a, 3, 5b, 7, and 12 were determined by single-crystal X-ray diffraction.

react with the lithium, sodium, and potassium salts of 1-(but-3-enyl)-2,3,4,5-tetramethylcyclopentadiene, yielding [(CH 2 dCHCH 2 CH 2 C 5 Me 4 ) 2 LnCl] 2 (Ln ) Y (3a), Sm (3b), Lu (3c)) and (CH 2 dCHCH 2 CH 2 C 5 Me 4 ) 2 Yb (6), respectively. The monomeric THF adducts (CH 2 dCHCH 2 CH 2 C 5 Me 4 ) 2 LnCl(THF) (Ln ) Y (2a), Sm (2b)) crystallize from hexane. Li[C 5 Me 4 CH 2 CH 2 CH 2 CHdCH 2 ] reacts with SmCl 3 , yielding (CH 2 dCHCH 2 CH 2 CH 2 C 5 -Me 4 ) 2 SmCl(THF) (5b). The reaction of YCl 3 , SmCl 3 , and LuCl 3 with 1 equiv of M[C 5 Me 4 -CH 2 CH 2 CHdCH 2 ] followed by M[C 5 Me 5 ] (M ) Na, K) gives [(CH 2 dCHCH 2 CH 2 C 5 Me 4 )(C 5 - (9c)). The NaCl adduct (CH 2 dCHCH 2 CH 2 C 5 Me 4 )(C 5 Me 5 )-Y(µ-Cl) 2 Na(Et 2 O) 2 (8a) crystallizes from Et 2 O. The cyclopentadienyllanthanide halides 3a,b and 9b react with LiMe, LiCH(SiMe 3 ) 2 , and LiN(SiMe 3 ) 2 , forming the corresponding unstable alkyl derivatives (CH 2 dCHCH 2 CH 2 C 5 Me 4 ) 2 LnR (Ln ) Y, R ) Me (10a), CH(SiMe 3 ) 2 (11a); Ln ) Sm, R ) CH(SiMe 3 ) 2 (11b)), and (CH 2 dCHCH 2 CH 2 C 5 Me 4 )(C 5 Me 5 )YCH(SiMe 3 ) 2 (12a), as well as (CH 2 dCHCH 2 CH 2 C 5 Me 4 ) 2 SmN(SiMe 3 ) 2 (13b). 10a, 11a,b, and 12a have been characterized by mass spectrometry, whereas all data of 13b have been obtained. The trichlorides of Y, Sm, and Lu react with 2 equiv of the sodium and potassium salts of 1-(4-methylpent-3-enyl)-2,3,4,5-tetramethylcyclopentadiene, yielding [(Me 2 CdCHCH 2 CH 2 C 5 Me 4 ) 2 -LnCl] 2 (Ln ) Y (15a), Sm (15b), Lu (15c)) or with 1 equiv of M[C 5 Me 4 CH 2 CH 2 CHdCMe 2 ] followed by M[C 5 Me 5 ] (M ) Na, K), yielding [(Me 2 CdCHCH 2 CH 2 C 5 Me 4 )(C 5 Me 5 )LnCl] 2 (Ln ) Y (17a), Sm (17b), Lu (17c)). The monomeric NaCl adduct (Me 2 CdCHCH 2 CH 2 C 5 Me 4 )(C 5 -Me 5 )Lu(µ-Cl) 2 Na(OEt 2 ) 2 (16c) crystallizes from Et 2 O. The structures of 2a,b, 8a, 13b, and 16c were determined by single-crystal X-ray diffraction.

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Photoluminescence of sintered zinc orthosilicate doped with Al or Ti has been measured in the temperature range between 20 and 650 K, peak emissions being noted at 407 and 400 nm, respectively. The corresponding excitation spectra show peaks at 218 and 236 nm for Zn2SiO4:normalAl and at 218 and 232 nm for Zn2SiO4:normalTi . The 218 nm peak must be assigned to the excitation of the undoped zinc silicate where doping with Al as well as Ti effects an enhancement of this band. The two phosphors have different decay times at room temperature ( Zn2SiO4:normalAl,t≈10sec ; Zn2SiO4:normalTi,t≈10−3sec ). We observed the greatest quantum efficiency for the u.v.‐blue emission approximately at activator concentrations of 1 mol percent (m/o) Al or 0.6 m/o Ti. Deviations from the linear dependence of the luminescence intensity on the photoexcitation intensity are observed above 400 K.

YbI2(THF)2 reacts with two equivalents of K[C5Me4CH2CH2CH=CH2] yielding unsolvated (C5Me4CH2CH2CH=CH2)2Yb (1). The molecular structure shows both tethered olefins orientated toward the Yb center.

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