Download PDF
Synthesis 2008(16): 2594-2602  
DOI: 10.1055/s-2008-1067172
PAPER
© Georg Thieme Verlag Stuttgart ˙ New York

Asymmetric Synthesis of (2S,3S)- and (2R,3R)-α,β-Dialkyl-α-amino Acids via Alkylation of Chiral Nickel(II) Complexes of Aliphatic α-Amino Acids with Racemic α-Alkylbenzyl Bromides

Vadim A. Soloshonok*, Thomas U. Boettiger, Shawna B. Bolene
Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK 73019, USA
Fax: +1(405)3256111; e-Mail: vadim@ou.edu;
Further Information

Publication History

Received 30 March 2008
Publication Date:
08 July 2008 (online)

   Permissions and Reprints All articles of this category
Preview

Abstract

This study has demonstrated that the stereochemical outcome of the direct alkylation of nickel(II) complexes derived from chiral Schiff bases of glycine, alanine, 2-aminobutyric acid, and leucine with racemic α-methylbenzyl bromide depends on the steric bulk of the corresponding amino acid residue. In particular, the alkylation of the alanine complex was found to proceed with a synthetically useful level (90% de) of stereoselectivity offering a concise synthesis of enantiomerically pure (2S,3S)- or (2R,3R)-α,β-dimethylphenylalanines.

Key words

sterically constrained amino acids - alkylation - asymmetric synthesis - kinetic resolution

    References

  • 2 Soloshonok VA. Cai C. Hruby VJ. Meervelt L. Tetrahedron  1999,  55:  12045 
    CrossrefSearch in Google Scholar
  • 3a Fluorine-Containing Amino Acids. Synthesis and Properties   Kukhar’ VP. Soloshonok VA. Wiley; Chichester: 1994. 
  • 3b O’Hagan D. Schaffrath C. Cobb S. Hamilton JTG. Murphy CD. Nature  2002,  416:  279 
    Search in Google Scholar
  • 4a Wang L. Brock A. Herberich B. Schultz PG. Science  2001,  292:  498 
    Search in Google Scholar
  • 4b Deiters A. Cropp AT. Mukherji M. Chin JW. Anderson CJ. Schultz PG. J. Am. Chem. Soc.  2003,  125:  11782 
    Search in Google Scholar
  • 5 Hruby VJ. Lu G. Haskell-Luevano C. Shenderovich MD. Biopolymers (Peptide Science)  1997,  43:  219 ; and references cited therein
    CrossrefPubMedSearch in Google Scholar
  • 6 Gibson SE. Guillo N. Tozer MJ. Tetrahedron  1999,  55:  585 ; and references cited therein
    CrossrefSearch in Google Scholar
  • For monographs, see:
  • 7a Molecular Conformation and Biological Interactions   Balaram P. Ramaseshan S. Indian Academy of Science; Bangalore: 1991. 
  • 7b Advances in Amino Acid Mimetics and Peptidomimetics   Abell A. JAI Press Inc.; Greenwich: 1999.  p.191-220  
  • 8 Special issue on Protein Design, Guest Editor DeGrado WF. Chem. Rev.  2001,  101:  3025-3032 
    Search in Google Scholar
  • 9 For a recent collection of papers, see the Special Issue: Asymmetric Synthesis of Novel Sterically Constrained Amino Acids, Tetrahedron Symposia-in-Print # 88; Guest Editors Hruby VJ. Soloshonok VA. Tetrahedron  2001,  57:  6329-6650 
    Search in Google Scholar
  • For general reviews on asymmetric synthesis of α-amino acids, see:
  • 10a Cativiela C. Diaz-de-Villegas MD. Tetrahedron: Asymmetry  1998,  9:  3517 
    Search in Google Scholar
  • 10b Cativiela C. Diaz-de-Villegas MD. Tetrahedron: Asymmetry  2000,  11:  654 
    Search in Google Scholar
  • 10c Duthaler RO. Tetrahedron  1994,  50:  1539 
    Search in Google Scholar
  • 10d Nájera C. Sansano JM. Chem. Rev.  2007,  107:  4584 
    Search in Google Scholar
  • 11 Gomez-Catalan J. Perez JJ. Jimenez AI. Cativiela C. J. Pept. Sci.  1999,  5:  251 
    CrossrefSearch in Google Scholar
  • 12a Masumoto S. Usuda H. Suzuki M. Kanai M. Shibasaki M. J. Am. Chem. Soc.  2003,  125:  5634 
    Search in Google Scholar
  • 12b Kato N. Suzuki M. Kanai M. Shibasaki M. Tetrahedron Lett.  2004,  45:  3147 
    Search in Google Scholar
  • 12c Kato N. Suzuki M. Kanai M. Shibasaki M. Tetrahedron Lett.  2004,  45:  3153 
    Search in Google Scholar
  • 12d Fujimori I. Mita T. Maki K. Shiro M. Sato A. Furusho S. Kanai M. Shibasaki M. J. Am. Chem. Soc.  2006,  128:  16438 
    Search in Google Scholar
  • 12e Fujimori I. Mita T. Maki K. Shiro M. Sato A. Furusho S. Kanai M. Shibasaki M. Tetrahedron  2007,  63:  5820 
    Search in Google Scholar
  • 13a Ooi T. Uematsu Y. Maruoka K. J. Am. Chem. Soc.  2006,  128:  2548 
    Search in Google Scholar
  • 13b Ooi T. Uematsu Y. Fujimoto J. Fukumoto K. Maruoka K. Tetrahedron Lett.  2007,  48:  1337 
    Search in Google Scholar
  • 13c Ooi T. Kato D. Inamura K. Ohmatsu K. Maruoka K.   , 
  • 14a Ohfune Y. Shinada T. Eur. J. Org. Chem.  2005,  5127 
  • 14b Ohfune Y. Shinada T. Bull. Chem. Soc. Jpn.  2003,  76:  1115 
    Search in Google Scholar
  • 14c Namba K. Shinada T. Teramoto T. Ohfune Y. J. Am. Chem. Soc.  2000,  122:  10708 
    Search in Google Scholar
  • 14d Moon S.-H. Ohfune Y. J. Am. Chem. Soc.  1994,  116:  7405 
    Search in Google Scholar
  • 15a Davis FA. Liang C.-H. Liu H. J. Org. Chem.  1997,  62:  3796 
    Search in Google Scholar
  • 15b Davis FA. Liu H. Zhou P. Fang T. Reddy GV. Zhang Y. J. Org. Chem.  1999,  64:  7559 
    Search in Google Scholar
  • 16a Fitzi R. Seebach D. Tetrahedron  1988,  44:  5277 
    Search in Google Scholar
  • 16b Kazmierski WM. Urbanczyk-Lipkowska Z. Hruby VJ. J. Org. Chem.  1994,  59:  1789 
    Search in Google Scholar
  • 17 Soloshonok VA. Tang X. Hruby VJ. Meervelt LV. Org. Lett.  2001,  3:  341 
    CrossrefPubMedSearch in Google Scholar
  • For selected recent reviews, see:
  • 18a Calmes M. Daunis J. Amino Acids  1999,  16:  215 
    Search in Google Scholar
  • 18b Bouifraden S. Drouot C. El Hadrami M. Guenoun F. Lecointe L. Mai N. Paris M. Pothion C. Sadoune M. Sauvagnat B. Amblard M. Aubagnac JL. Calmes M. Chevallet P. Daunis J. Enjal-bal C. Fehrentz JA. Lamaty F. Lavergne JP. Lazaro R. Rolland V. Roumestant ML. Viallefont P. Vidal Y. Martinez J. Amino Acids  1999,  16:  345 
    Search in Google Scholar
  • 18c Sutherland A. Willis CL. Nat. Prod. Rep.  2000,  17:  621 
    Search in Google Scholar
  • 18d Beller M. Eckert M. Angew. Chem. Int. Ed.  2000,  39:  1010 
    Search in Google Scholar
  • 18e Kawabata T. Fuji K. Synth. Org. Chem. Jpn.  2000,  58:  1095 
    Search in Google Scholar
  • 18f Kazmaier U. Maier S. Zumpe FL. Synlett  2000,  1523 
  • 18g Yao SL. Saaby S. Hazell RG. Jorgensen KA. Chem. Eur. J.  2000,  6:  2435 
    Search in Google Scholar
  • 18h Abellan T. Chinchilla R. Galindo N. Guillena G. Najera C. Sansano JM. Eur. J. Org. Chem.  2000,  2689 
  • 18i Rutjes FPJT. Wolf LB. Schoemaker HE. J. Chem. Soc., Perkin Trans. 1  2000,  4197 
  • 18j Shioiri T. Hamada Y. Synlett  2001,  184 
  • 18k Williams RM. Synthesis of Optically Active α-Amino Acids   Pergamon Press; Oxford: 1989. 
  • 19a Belokon YN. Janssen Chim. Acta  1992,  10 (2):  4 
    Search in Google Scholar
  • 19b Belokon YN. Pure Appl. Chem.  1992,  64:  1917 
    Search in Google Scholar
  • 20 Ueki H. Ellis TK. Martin CH. Bolene SB. Boettiger TU. Soloshonok VA. J. Org. Chem.  2003,  68:  7104 
    CrossrefPubMedSearch in Google Scholar
  • 21a Andronova IG. Maleev VI. Ragulin VV. Il’in MM. Tsvetkov EN. Belokon’ YuN. Zh. Obshch. Khim.  1996,  66:  1096 
    Search in Google Scholar
  • 21b Tararov VI. Savel’eva TF. Kuznetsov NYu. Ikonnikov NS. Orlova SA. Belokon’ YuN. North M. Tetrahedron: Asymmetry  1997,  8:  79 
    Search in Google Scholar
  • 21c Sagiyan AS. Dzhamgaryan SM. Grigoryan GL. Kagramanyan SR. Ovsepyan GTs. Grigoryan SK. Belokon’ YuN. Khimich. Zh. Armenii  1996,  49:  75 
    Search in Google Scholar
  • 21d Sagiyan AS. Grigoryan SK. Dzhamgaryan SM. Grigoryan GL. Belokon’ YuN. Khimich. Zh. Armenii  1996,  49:  142 
    Search in Google Scholar
  • 21e Belokon’ YN. Kochetkov KA. Ikonnikov NS. Strelkova TV. Harutyunyan SR. Saghiyan AS. Tetrahedron: Asymmetry  2001,  12:  481 
    Search in Google Scholar
  • 21f Larionov OV. Savel’eva TF. Kochetkov KA. Ikonnokov NS. Kozhushkov SI. Yufit DS. Howard JAK. Khrustalev VN. Belokon YN. de Meijere A. Eur. J. Org. Chem.  2003,  869 
  • 21g Belokon YN. Kochetkov KA. Borkin DA. Mendeleev Commun.  2003,  132 
  • 21h Belokon YN. Maleev VI. Savel’eva TF. Moskalenko MA. Pripadchev DA. Khrustalev VN. Vorontsov EV. Sagiyan AS. Babayan EP. Russ. Chem. Bull.  2005,  54:  981 
    Search in Google Scholar
  • 22a Soloshonok VA. Belokon YN. Kukhar VP. Chernoglazova NI. Saporovskaya MB. Bakhmutov VI. Kolycheva MT. Belikov VM. Izv. Akad. Nauk SSSR, Ser. Khim.  1990,  1630 
  • 22b Soloshonok VA. Kukhar VP. Galushko SV. Kolycheva MT. Rozhenko AB. Belokon YN. Izv. Akad. Nauk SSSR, Ser. Khim.  1991,  1166 
  • 22c Soloshonok VA. Kukhar VP. Batsanov AS. Galakhov MA. Belokon YN. Struchkov YT. Izv. Akad. Nauk SSSR, Ser. Khim.  1991,  1548 
  • 22d Soloshonok VA. Kukhar VP. Galushko SV. Rozhenko AB. Kuzmina NA. Kolycheva MT. Belokon YN. Izv. Akad. Nauk SSSR, Ser. Khim.  1991,  1906 
  • 22e Soloshonok VA. Svistunova NY. Kukhar VP. Gudima AO. Kuzmina NA. Belokon YN. Izv. Akad. Nauk SSSR, Ser. Khim.  1992,  117 
  • 22f Soloshonok V. A., Svistunova N. Y., Kukhar V. P., Solodenko V. A., Kuzmina N. A., Rozhenko A. B., Galushko S. V., Shishkina I. P., Gudima A. O., Belokon Y. N.; Izv. Akad. Nauk SSSR, Ser. Khim.; 1992, 397
  • 22g Soloshonok VA. Svistunova NY. Kukhar VP. Kuzmina NA. Belokon YN. Izv. Akad. Nauk SSSR, Ser. Khim.  1992,  687 
  • 22h Soloshonok VA. Belokon YN. Kuzmina NA. Maleev VI. Svistunova NY. Solodenko VA. Kukhar VP. J. Chem. Soc., Perkin Trans. 1  1992,  1525 
  • 22i Kukhar VP. Belokon YN. Svistunova NY. Soloshonok VA. Rozhenko AB. Kuzmina NA. Synthesis  1993,  117 
  • 22j Soloshonok VA. Svistunova NY. Kukhar VP. Kuzmina NA. Popov VI. Belokon YN. Izv. Akad. Nauk SSSR, Ser. Khim.  1993,  786 
  • 22k Soloshonok VA. Kukhar VP. Galushko SV. Svistunova NY. Avilov DV. Kuzmina NA. Raevski NI. Struchkov YT. Pisarevsky AP. Belokon YN. J. Chem. Soc., Perkin Trans. 1  1993,  3143 
  • 22l Kukhar VP. Luik AI. Soloshonok VA. Svistunova NY. Skryma RN. Rybalchenko VV. Belokon YN. Kuzmina NA. Khim. Pharm. Zh.  1994,  27:  35 
    Search in Google Scholar
  • 22m Soloshonok VA. Avilov DV. Kukhar VP. Tararov VI. Saveleva TF. Churkina TD. Ikonnikov NS. Kochetkov KA. Orlova SA. Pysarevsky AP. Struchkov YT. Raevsky NI. Belokon YN. Tetrahedron: Asymmetry  1995,  6:  1741 
    Search in Google Scholar
  • 22n Soloshonok VA. Gerus II. Yagupolskii YL. Kukhar VP. Zh. Org. Khim.  1987,  23:  2308 ; Chem. Abstr. 1988, 109, 55185
    Search in Google Scholar
  • 22o Basyuk VA. Gromovoi TY. Chuiko AA. Soloshonok VA. Kukhar VP. Synthesis  1992,  449 
  • 23a Soloshonok VA. Avilov DV. Kukhar VP. Tetrahedron: Asymmetry  1996,  7:  1547 
    Search in Google Scholar
  • 23b Soloshonok VA. Avilov DV. Kukhar VP. Tetrahedron  1996,  52:  12433 
    Search in Google Scholar
  • 23c Soloshonok VA. Avilov DV. Kukhar’ VP. Meervelt LV. Mischenko N. Tetrahedron Lett.  1997,  38:  4671 
    Search in Google Scholar
  • 23d Soloshonok VA. Avilov DV. Kukhar’ VP. Meervelt LV. Mischenko N. Tetrahedron Lett.  1997,  38:  4903 
    Search in Google Scholar
  • 23e Soloshonok VA. Cai C. Hruby VJ. Meervelt LV. Mischenko N. Tetrahedron  1999,  55:  12031 
    Search in Google Scholar
  • 23f Soloshonok VA. Cai C. Hruby VJ. Meervelt LV. Tetrahedron  1999,  55:  12045 
    Search in Google Scholar
  • 23g Soloshonok VA. Cai C. Hruby VJ. Tetrahedron: Asymmetry  1999,  10:  4265 
    Search in Google Scholar
  • 23h Soloshonok VA. Cai C. Hruby VJ. Tetrahedron Lett.  2000,  41:  135 
    Search in Google Scholar
  • 23i Soloshonok VA. Cai C. Hruby VJ. Org. Lett.  2000,  2:  747 
    Search in Google Scholar
  • 23j Qiu W. Soloshonok VA. Cai C. Tang X. Hruby VJ. Tetrahedron  2000,  56:  2577 
    Search in Google Scholar
  • 23k Soloshonok VA. Cai C. Hruby VJA. Angew. Chem. Int. Ed.  2000,  39:  2172 
    Search in Google Scholar
  • 23l Tang X. Soloshonok VA. Hruby VJ. Tetrahedron: Asymmetry  2000,  11:  2917 
    Search in Google Scholar
  • 23m Soloshonok VA. Cai C. Hruby VJ. Meervelt LV. Yamazaki T. J. Org. Chem.  2000,  65:  6688 
    Search in Google Scholar
  • 23n Soloshonok VA. Cai C. Hruby VJ. Tetrahedron Lett.  2000,  41:  9645 
    Search in Google Scholar
  • 23o Cai C. Soloshonok VA. Hruby VJ. J. Org. Chem.  2001,  66:  1339 
    Search in Google Scholar
  • 23p Soloshonok VA. Tang X. Hruby VJ. Tetrahedron  2001,  57:  6375 
    Search in Google Scholar
  • 23q Soloshonok VA. Curr. Org. Chem.  2002,  6:  341 
    Search in Google Scholar
  • 23r Ellis TK. Hochla VM. Soloshonok VA. J. Org. Chem.  2003,  68:  4973 
    Search in Google Scholar
  • 23s Taylor SM. Yamada T. Ueki H. Soloshonok VA. Tetrahedron Lett.  2004,  45:  9159 
    Search in Google Scholar
  • 23t Soloshonok VA. Cai C. Yamada T. Ueki H. Ohfune Y. Hruby VJ. J. Am. Chem. Soc.  2005,  127:  15296 
    Search in Google Scholar
  • 23u Soloshonok VA. Yamada T. Ueki H. Moore AM. Cook TK. Arbogast KL. Soloshonok AV. Martin CH. Ohfune Y. Tetrahedron  2006,  62:  6412 
    Search in Google Scholar
  • 23v Soloshonok VA. Ueki H. J. Am. Chem. Soc.  2007,  129:  2426 
    Search in Google Scholar
  • 24a Fishwick CWG. Sanderson JM. Findlay JBC. Tetrahedron Lett.  1994,  35:  4611 
    Search in Google Scholar
  • 24b Chen B.-H. Nie J.-Y. Singh M. Pike VW. Kirk KL. J. Fluorine Chem.  1995,  75:  93 
    Search in Google Scholar
  • 24c Kliukiene R. Maroziene A. Stumbreviciute Z. Karpavicius K. Chemija  1996,  3:  76 
    Search in Google Scholar
  • 24d Mosevich IK. Kuznetsova OF. Fedorova OS. Korsakov MV. Radiochemistry (Moscow)  1996,  38:  511 
    Search in Google Scholar
  • 24e Jirman J. Nadvornik M. Sopkova J. Popkov A. Magn. Reson. Chem.  1998,  36:  351 
    Search in Google Scholar
  • 24f Collet S. Bauchat P. Danion-Bougot R. Danion D. Tetrahedron: Asymmetry  1998,  9:  2121 
    Search in Google Scholar
  • 24g Popkov A. Jirman J. Nadvornik M. Manorik PA. Collect. Czech. Chem. Commun.  1998,  63:  990 
    Search in Google Scholar
  • 24h Popkov AN. Nadvornik M. Iirman I. Sopkova Ya. Manorik PA. Fedorenko MA. Russ. J. Gen. Chem.  1998,  68:  1242 
    Search in Google Scholar
  • 24i Mosevich IK. Kuznetsova OF. Vasil’ev DA. Anichkov AA. Korsakov MV. Radiochemistry (Moscow)  1999,  41:  273 
    Search in Google Scholar
  • 24j Collet S. Carreaux F. Boucher J.-L. Pethe S. Lepoivre M. Danion-Bougot R. Danion D. J. Chem. Soc., Perkin Trans. 1  2000,  177 
  • 24k Debache A. Collet S. Bauchat P. Danion D. Euzenat L. Hercouet A. Carboni B. Tetrahedron: Asymmetry  2001,  12:  761 
    Search in Google Scholar
  • 24l Nadvornik M. Popkov A. Green Chem.  2002,  4:  71 
    Search in Google Scholar
  • 24m Gu X. Tang X. Cowell S. Ying J. Hruby VJ. Tetrahedron Lett.  2002,  43:  6669 
    Search in Google Scholar
  • 24n Hashimoto M. Hatanaka Y. Sadakane Y. Nabeta K. Bioorg. Med. Chem. Lett.  2002,  12:  2507 
    Search in Google Scholar
  • 24o Zhang J. Xiong C. Ying J. Wang W. Hruby VJ. Org. Lett.  2003,  5:  3115 
    Search in Google Scholar
  • 24p Chaykovski MM. Bae LC. Cheng M.-C. Murray JH. Tortolani KE. Zhang R. Seshadri K. Findlay JHBC. Hsieh S.-Y. Kalverda AP. Homans SW. Brown JM. J. Am. Chem. Soc.  2003,  125:  15767 
    Search in Google Scholar
  • 24q Gu X. Ndungu JM. Qiu W. Ying J. Carducci MD. Wooden H. Hruby VJ. Tetrahedron  2004,  60:  8233 
    Search in Google Scholar
  • 24r Hao B. Zhao G. Kang PT. Soares JA. Ferguson TK. Gallucci J. Krzycki JA. Chan MK. Chem. Biol.  2004,  11:  1317 
    Search in Google Scholar
  • 24s Ouchi H. Kumagai M. Sakurada S. Takahata H. Heterocycles  2004,  64:  505 
    Search in Google Scholar
  • 24t Ghalit N. Poot AJ. Fuerstner A. Rijkers DTS. Liskamp RMJ. Org. Lett.  2005,  7:  2961 
    Search in Google Scholar
  • 24u Pessoa JC. Correia I. Galvao A. Gameiro A. Felix V. Fiuza E. Dalton Trans.  2005,  2312 
  • 24v Vadon-Legoff S. Dijols S. Mansuy D. Boucher J.-L. Org. Process Res. Dev.  2005,  9:  677 
    Search in Google Scholar
  • 24w Popkov A. Cisarova I. Sopkova J. Jirman J. Lycka A. Kochetkov KA. Collect. Czech. Chem. Commun  2005,  70:  1397 
    Search in Google Scholar
  • 24x Saghiyan AS. Dadayan SA. Petrosyan SG. Manasyan LL. Geolchanyan AV. Djamgaryan SM. Andreasyan SA. Maleev VI. Khrustalev VN. Tetrahedron: Asymmetry  2006,  17:  455 
    Search in Google Scholar
  • 24y Saghiyan AS. Geolchanyan AV. Synth. Commun.  2006,  36:  3667 
    Search in Google Scholar
  • 24z Langer V. Popkov A. Nadvornik M. Lycka A. Polyhedron  2007,  26:  911 
    Search in Google Scholar
  • 26 For the complex containing (2S,3R)-3-phenylglutamic acid, the α-proton appears at δ = 4.14 (J α H, β H = 3.7 Hz); for the complex containing (2S,3S)-3-phenylglutamic acid, the α-proton is at δ = 4.07 (J α H, β H = 7.0 Hz); for details, see: Belokon’ YuN. Bulychev AG. Ryzhov MG. Vitt SV. Batsanov AS. Struchkov YuT. Bakhmutov VI. Belikov VM. J. Chem. Soc., Perkin Trans. 1  1986,  1865 
    Crossref
  • 27 Dharanipragada R. VanHulle K. Bannister A. Bear S. Kennedy L. Hruby VJ. Tetrahedron  1992,  48:  4733 
    CrossrefSearch in Google Scholar
  • 28a Soloshonok VA. Cai C. Hruby VJ. Tetrahedron: Asymmetry  1999,  10:  4265 
    Search in Google Scholar
  • 28b Soloshonok VA. Cai C. Hruby VJ. Tetrahedron Lett.  2000,  41:  135 
    Search in Google Scholar
  • 28c Soloshonok VA. Cai C. Hruby VJ. Org. Lett.  2000,  2:  747 
    Search in Google Scholar
  • 28d Soloshonok VA. Cai C. Hruby VJ. Angew. Chem. Int. Ed.  2000,  39:  2172 
    Search in Google Scholar
  • 28e Soloshonok VA. Cai C. Hruby VJ. Meervelt LV. Yamazaki T. J. Org. Chem.  2000,  65:  6688 
    Search in Google Scholar
  • 28f Soloshonok VA. Cai C. Hruby VJ. Tetrahedron Lett.  2000,  41:  9645 
    Search in Google Scholar
  • 28g Cai C. Soloshonok VA. Hruby VJ. J. Org. Chem.  2001,  66:  1339 
    Search in Google Scholar
  • 28h Soloshonok VA. Ueki H. Tiwari R. Cai C. Hruby VJ. J. Org. Chem.  2004,  69:  4984 
    Search in Google Scholar
  • 28i Cai C. Yamada T. Tiwari R. Hruby VJ. Soloshonok VA. Tetrahedron Lett.  2004,  45:  6855 
    Search in Google Scholar
  • 28j Soloshonok VA. Ueki H. Ellis TK. Tetrahedron Lett.  2005,  46:  941 
    Search in Google Scholar
  • 28k Soloshonok VA. Ueki H. Ellis TK. Yamada T. Ohfune Y. Tetrahedron Lett.  2005,  46:  1107 
    Search in Google Scholar
  • 28l Soloshonok VA. Ellis TK. Synlett  2006,  533 
  • 28m Ellis TK. Ueki H. Yamada T. Ohfune Y. Soloshonok VA. J. Org. Chem.  2006,  71:  8572 
    Search in Google Scholar
1

As we recently pointed out (see ref. 2), the terms unnatural, unusual, or nonproteinogenic, noncoded amino acids depend on the success of specific scientific achievements. For instance, amino acids containing the most xenobiotic element fluorine were shown to be synthesized by microorganisms (see ref. 3), and also new amino acids can be added to genetic code of microorganisms (see ref. 4). Therefore, the time-independent term tailor-made, meaning rationally designed/synthesized amino acids, in the absence of a better definition, is used in this paper and generally recommended for use in the corresponding literature.

25

As shown previously (see refs. 21-23), CD and ORD spectra of Ni(II) complexes of this type in neutral solutions exhibit two maxima in the region of metal d-d transition (Cotton effects at 450 and 550 nm). In the ORD spectra, the sign of Cotton effects in this region strictly depends upon a conformation of the polycyclic system of chelate rings. Thus, in the case of complexes containing α-monosub-stituted α-amino acid, the pseudoaxial orientation of the amino acid side chain, corresponding to α-l configuration of α-amino acid, causes a Cotton effect with a positive sign at the 500-700 nm region and negative sign at 400-450 nm. Consequently, a pseudoequatorial orientation of the amino acid side chain brings about opposite signs of the Cotton effects at 400-450 (positive) and at the 500-700 nm (negative) regions. As established in numerous studies, this general trend is not influenced by the structure and nature of the α-amino acid side chain, and the configuration of stereogenic centers within it.