1- tert.-Butyl-5-ethoxycarbonyl-4-

Di-tert.-butyl-(ethoxycarbonyl-methyl)- E2, 22 Dibutyl-( 1-hydroxy- l-methyl-2-oxo-propyl)-E2, 261... 

N-[ 1 (S)-ethoxycarbonyl-3-phenylpropyl]-L-olanine tert-butyl ester (l)... 

To overcome these difficulties in the selective deprotection and chain extension, several carboxyl-protecting groups, namely, allyl (16,32), benzyl (43,44), tert-butyl (42), 2-bromoethyl (45), 2-chloroethyl (45), heptyl (46), 4-nitrophenyl (47,48), and pentafluorophenyl (49) for L-serine/L-threonine have been introduced or applied. Similarly, amino-protecting groups for L-serine/L-threonine that have proved useful for the synthesis of glycopeptides are tm-butyloxycarbonyl (50), 9-fluorenylmethoxycarbonyl (43,44,48), 2-(2-pyridyl)ethoxycarbonyl (51), 2-(4-pyridyl)ethoxycarbonyl (44,52), and 2-triphenylphosphonioethoxycarbonyl (53). Some applications of these groups have been discussed in earlier reviews (7-11). 

To further exploit the potential usefiilness of this new family of clusters, monoadduct 54 was saponified into 55 (0.05 M NaOH, quant) and condensed to L-lysine methyl ester using 2-ethoxy-l-ethoxycarbonyl-l,2-dihydroquinoline (EEDQ) to give extended dimer 56 in 50 % yield together with monoadduct in 15 % yield [75]. Additionally, tert-butyl thioethers 52 could be transformed into thiols by a two step process involving 2-nitrobenzenesulfenyl chloride (2-N02-PhSCl, HOAc, r.t, 3h, 84%) followed by disulfide reduction with 2-mercaptoethanol (60%). Curiously, attempts to directly obtain these thiolated telomers by reaction with thioacetic acid f ed. These telomers were slightly better ligands then lactose in inhibition of binding of peanut lectin to a polymeric lactoside [76]. 

C(CII,), -"0 CH3 CF3 cooc2h5 l-tert.-Butyl-4-(4-methyl-phenyl)-5-trifluormethyl-... l-tert.-Butyl-5-ethoxycarbonyl-4-(4-methyl-phenyl)-... 99 87... 

ATP, adenosine 5 -triphosphate BH4, 5,6,7,8-tetrahydrobiopterin BMPO, 5- er -butoxycarbonyl-5-pyrroline A-oxide DBNBS, 3,5-dibromo-4-nitrosoben-zene sulfonate DEPMPO, 5-diethoxyphosphoryl-5-methyl-l-pyrroline A-ox-ide DMPO, 5,5-dimethyl- 1-pyrroline A-oxide EMPO, 5-ethoxycarbonyl-5-methyl-l-pyrroline A-oxide GSH, glutathione (y-L-glutamyl-L-cysteinyl-glycine) HRP, horseradish peroxidase MNP, 2-methyl-2-nitrosopropane MPO, myeloperoxidase NAD(P)H, fl-nicotinamine adenine dinucleotide (3 -phosphate), reduced from NMDA, A-methyl-D-aspartic acid PBN, N-tert-butyl-a-phenylnitrone PMN, polymorphonuclear lymphocyte POBN, a-(4-pyridyl-l-oxide)-A-fer -butylnitrone SOD, superoxide dismutase TEMP,... 

Abbreviations AllocOSu, allyloxycarbonyl-A-hydroxysuccinimide BCIP, 5-bromoA-chloro-3-indolyl Boc, tert-butyloxycarbonyl tBu, tert-butyl DCM, dichloromethane Dde, l-(4,4-dimethyl-2,6-dioxocyclohex-l-ylidene)ethyl Ddz, a, a-dimethyl-3,5-dimethoxyben-zyloxycarbonyl DIC, A,A -diisopropylcarbodiimide DIEA, A,fV-diisopropylethylamine DMF, iV,./V-dimethylformamide FmocOSu, 9-fluorenylmethyloxycarbonyl-AMiydroxysucci-nimide OBOC, one-bead one-compound PBS, phosphate-buffered saline Pmc, 2,2,5,7,8-pentamethylchroman-6-sulfonyl PTH, phenylthiohydantoin RR, relative reactivities Teoc, 2-(trimethylsilyl)ethoxycarbonyl TFA, trifluoroacetic acid Trt, trityl. 

Hydroxylamin N-tert.-Butyl-N-(2,2,2-trichlor-ethoxycarbonyl)-EI6a, 284 (O-Deacetylis.)... 

E19a, 1243 (C-N02 + C-M) 1-Buten 2-Nitro-l-pyrrolidino-E15/2, 1381 (NH-R - NR2) Carbodiimid N-tert.-Butyl-N -ethoxycarbonyl- E4, 1265 (aus Thioharnstoff-Der.) Cyclohexan l,3-Dimethyl-5-... 

Keten Ethoxycarbonyl- -tert.-butylimin E15/3, 2607 (R2CH-CN + R —Cl) Malonsaure, tert.-Butyl- -ethyl-ester-nitril VIII, 621... 

Oxa-4-aza-bicyclo]3.1. Olhexane (7R,3R,5S)-3-tert.-Butyl-4-methoxycarbonyl- E21c, 3197 9-Oxa-l-aza-bicyclo]4.3.01nonan 7-Ethoxycarbonyl- Elba, 389 (En + R2N-OH)... 

Oxo-4-aza-bicyclo 3.I.O hexane 3-tert.-Butyl-6-ethoxycarbonyl-4-methoxycarbonyl- E21c, 3231 (1,3-Oxazol + N2CH-COOR)... 

Thiobernsteinsaure 2(bzw. 3)-Ethoxycarbonyl- l-tert.-butyl-peroxyester-4-S-ethylester E13/1, 798 (R-COOH + R-O-OH)... 

In 2004, Kim and coworker developed their own cinchona PTCs containing a specific bulky aryl moiety, 3,5-di-tert-butyl-4-methoxybenzyl group, such as 75, and applied them to the asymmetric a-alkylation of the cyclic [i-kctocstcrs, for example, 2-(ethoxycarbonyl)-l-indanone73 (n — 0) or 2-(cthoxycarbonyl)-1 -tctralonc 73 (n— 1) as shown in Scheme 6.22 [47]. The enantioselectivities showed a considerable variation (44—99% ee) depending on the nature of electrophile. 

---