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Helvetica Chimica Acta ± Vol. 88 (2005)
A NaOAc buffer, prepared by mixing AcOH (2.9 ml) and 2m NaOH (4.55 ml) in H2O (900 ml) and MeOH
(100 ml); eluent B MeOH. Prep. HPLC: Varian Prostar system, equipped with two Prostar-215 pumps and a
Prostar-320 UV/VIS detector; Waters XTerra-Prep-RP8 column (5 mm particle size, 30 Â 100 mm); flow rate
30 ml/min. After prep. HPLC purification, the cob(III)alamin derivatives were desalted by applying an aqueous
soln. of the compound to a Chromafix RP18ec cartridge, followed by thorough rinsing with H2O. The desalted
product was then eluted with MeOH, the solvent evaporated, and the product dried under high vacuum. IR
Spectra: nÄ in cmÀ1. 1H-, 13C-, and 31P-NMR Spectra: Varian Gemini-2000 (1H at 300.08 MHz) and Bruker DRX-
500 (1H at 500.25 MHz) spectrometer; d(H) and d(C), referenced to SiMe4, by using the d(C) or residual d(H)
of the deuterated solvents as internal standards; d(P) referenced against 0.1m H3PO4 in H2O; d in ppm, J in Hz.
Electrospray-ionization (ESI) MS: Merck-Hitachi M-8000 spectrometer; positive-ion mode; MeOH as solvent;
in m/z. Elemental analyses: Leco CHNS-932 elemental analyzer.
(OC-6-44)(S-Benzyl-l-cysteinato-kN,kO,kS)tricarbonylrhenium(I) (4). A mixture of [Et4N]2[ReBr3-
(CO)3], (3; 100 mg, 0.130 mmol) and S-benzyl-l-cysteine (2; 28 mg, 0.132 mmol) in 1m aq. NaHCO3 (10 ml)
was heated at 708 for 14 h. During this period, a white precipitate formed, which was filtered off, washed with
H2O, and dried in vacuo: 53 mg (85%) of 4. X-Ray-quality crystals were grown by slow evaporation of a H2O/
MeOH 1:4 (v/v) soln. IR (KBr): 2030s, 1898s (br.). 1H-NMR (300.08 MHz, CD3OD): 7.37 (s, Ph); 4.28 (s,
PhCH2); 4.02 (m, HÀC(a)); 2.61 (m, CH2(b)). 13C-NMR (75.47 MHz, CD3OD): 195.5, 195.0, 193.4 (3 CO),
181.3 (CO); 135.2, 131.2, 130.4, 130.4, 130.2, 109.9 (PhCH2); 59.3; 41.6; 30.5. (CO). ESI-MS: 481.7 ([M
H] ). Anal. calc. for C13H12O5ReS: C 32.49, H 2.52, N 2.92; found: C 32.86, H 2.89, H 2.83.
S-{3-{[(9H-Fluoren-9-ylmethoxy)carbonyl]amino}propyl}-N-[(tert-butoxy)carbonyl]-l-cysteine Methyl
Ester (10). To a soln. of KOH (56 mg, 1.0 mmol) in DMSO (10 ml) was added a solution of N-[(tert-
butoxy)carbonyl]-l-cysteine methyl ester (8; 235mg, 1.0 mol) in DMSO (2 ml). To this mixture was added a
soln. of Fmoc-NH-(CH2)3-I (9; 406 mg, 1.0 mmol) in DMSO (2 ml). The mixture was stirred at r.t. for 4 h. Then
2m NaHCO3 (ca. 50 ml) was added, the mixture extracted with AcOEt (3 Â 40 ml), the combined org. extract
washed with sat. NaCl soln. (3 Â 30 ml), dried (Na2SO4), and evaporated, and the residue purified by column
chromatography (AcOEt/hexane): 426 mg (83%) of 10. White solid. 1H-NMR (300.08 MHz, CD3CN): 7.82 (ꢂdꢃ,
2 arom. H); 7.63 (ꢂdꢃ, 2 arom. H); 7.41 (ꢂtꢃ, 3 arom. H); 7.33 (ꢂdꢃ, 2 arom. H); 5.68 (br., NH); 4.32 (m, CH2CH,
HÀC(a)), 4.20 (d, 3J(H,H) 6.3, CH); 3.63 (s, MeO); 3.13 (m, 2 H, CH2CH2): 2.90 (m, 1 HÀC(b)); 2.81 (m, 1
HÀC(b)); 2.51 (m, 2 H, CH2CH2); 1.68 (m, CH2CH2CH2); 1.39 (s, tBu). 13C-NMR (75.47 MHz; CDCl3): 171.8
(COOMe); 156.6, 155.4 (2 CO); 144.1, 141.4, 127.8, 127.1, 125.1, 120.0 (6 arom. C); 80.2 (quat. C); 66.5, 53.0,
52.5, 47.2, 39.4, 34.6, 29.5, 29.1, 28.2 (Me3C). ESI-MS: 514.4 (M ), 537.2 ([M Na] ), 1050.1 ([2M Na] ).
Anal. calc. (%) for C27H34N2O6S: C 63.01, H 6.66, N 5.44; found: C 63.28, H 6.41, N 5.49.
N-[(tert-Butoxy)carbonyl]-S-{3-[cyanocob(III)alamin-Nb-yl]propyl}-l-cysteine Methyl Ester (11). A soln.
of 7 (51.4 mg, 0.1 mmol) in DMF/Et2NH 2 :1 (3 ml) was stirred at r.t. for 1 h. Thereafter, the solvent was
evaporated. To the residue was added a soln. of cyanocob(III)alamin-b-acid (6; 20 mg, 14.8 mmol) in DMSO
(0.5ml) and DMF (4 ml). Subsequently were added Et 3N (1 ml) and TBTU (32 mg). After stirring at r.t. for
45min, the mixture was evaporated. Purification by prep. HPLC afforded 11 (14 mg, 61%). Red solid. 13C-NMR
(125.8 MHz, CD3OD1): 181.7; 180.3; 177.8; 177.7; 176.8; 175.7; 175.5; 174.8; 174.8; 174.5; 173.5; 167.3; 167.0;
158.0; 143.6; 138.4; 135.8; 133.9; 131.6; 118.0; 112.7; 108.9; 105.3; 95.8; 88.1; 86.6; 83.9; 83.8 (d, J(P,C) 5.9);
81.0; 76.5( d, J(P,C) 3.4); 75.6; 73.7 (d, J(P,C) 6.0); 70.9; 62.8; 60.5; 57.8; 57.1; 55.2; 53.1; 52.7; 49.9; 46.9 (d,
J(P,C) 4.4); 44.1; 43.2; 40.3; 39.6; 37.0; 35.5; 34.8; 33.7; 33.2; 33.2; 32.5; 30.7; 30.3; 29.8; 28.9; 27.7; 27.6; 21.2;
20.7; 20.5; 20.3 (d, J(P,C) 2.9); 20.1; 17.7; 17.2; 16.5; 16.2. 31P-NMR (202.5MHz, CD 3OD): 0.57. ESI-MS:
1630.4 ([M H] , C75H109CoN15O18PS ; calc. 1629.7).
S-{3-[Cyanocob(III)alamin-Nb-yl]propyl}-l-cysteine Methyl Ester (12). Compound 11 (14 mg, 8.5 mmol)
was dissolved in CH2Cl2/CF3COOH 4 :1 (5ml) 0 8. After stirring for 1 h at 08, the mixture was evaporated. The
residue was purified by prep. HPLC: 12 (9 mg, 68%). Red solid. 13C-NMR (125.80 MHz, CD3OD1): 181.7; 180.3;
177.8; 177.7; 176.8; 175.7; 175.7; 175.5; 175.1; 174.8; 174.4; 167.3; 167.1; 143.6; 138.4; 135.8; 133.9; 131.6; 117.7;
112.7; 108.8; 105.3; 95.8; 95.8; 88.1; 86.5; 83.8; 76.5; 75.6; 73.7; 70.8; 62.8; 60.5; 57.7; 57.0; 55.2; 54.9; 52.9; 52.7;
50.0; 48.5; 46.9; 44.0; 43.1; 40.2; 39.5; 37.0; 36.9; 35.5; 33.6; 33.1; 32.5; 32.4; 30.8; 30.4; 30.1; 29.8; 27.7; 27.5; 21.1;
20.6; 20.5; 20.4; 20.3; 20.0; 17.6; 17.2; 16.5; 16.2. 31P-NMR (202.5MHz, CD 3OD): 1.24. ESI-MS: 1530.5 ([M
H] , C70H101CoN15O16PS ; calc. 1529.6).
S-{2-{{4-[Cyanocob(III)alamin-Nb-yl]butyl}amino}-2-oxoethyl}-l-cysteine (17). Nb-(4-Aminobutyl)cyano-
cob(III)alamin (15) (23 mg, 16.3 mmol), prepared by the method of Pathare et al. [17] for the dodecane analogue
[18], was dissolved in a phosphate buffer at pH 7.4. Iodoacetic acid succinimid-N-yl ester (1-[(iodoacetyl)oxy]-
pyrrolidine-2,5-dione; 14 mg; 50 mmol) were added, and the mixture was stirred for 45min at r.t. Subsequently,
l-cysteine (H-Cys-OH; 18 mg, 0.15mmol) was added, and the mixture was stirred for 45min. The mixture was