S.B. Deepthi et al. / Journal of Organometallic Chemistry 774 (2014) 26e34
31
3
H, 7.57; N, 8.09%; found: C, 51.68; H, 7.42; N, 7.84%; MS (ESIþ): (m/
z) ¼ 369 [M þ Na]þ.
4.75 (bs, 1H, BocNH), 4.95 (dd, JH,H ¼ 1.9 Hz and 5.9 Hz, 1H, H-4),
5.84 (d, 3JH,H ¼ 2.9 Hz, 1H, H-1), 6.71 (bs, 1H, CONH) ppm; 13C NMR
(CDCl3, 300 MHz):
d
11.28 (isoleuCH3), 15.61 (isoleuCH3), 24.78 (iso-
5-(N-Boc-L-alaninlyamido)-5-deoxy-1,2-O-isopropylidene-
a
-D-
leuCH2), 26.12 (CH3), 26.82 (CH3), 28.30 (BocCH3), 37.14 (isoleuCH),
49.22 (isoleuCH), 59.43 (C-5), 73.77 (C-2), 79.62 (BocC(CH3)3), 79.85
(C-3), 84.80 (C-4), 104.78 (C-1), 111.45 (C(CH3)2), 155.86 (BocCO),
175.04 (NHCO) ppm; Anal. calcd. for C19H34N2O7: C, 56.70; H, 8.51;
N, 6.96%; found C, 56.50; H, 8.26; N, 6.65%; MS (ESIþ): m/z ¼ 403
[M þ H]þ.
xylofuranose (3b)
24
White solid; yield: 0.31 g (87%); mp: 155e160 ꢂC; [
a]
¼ ꢀ11.45
D
(CHCl3, c 0.1); IR (KBr, ymax): 3301, 2987, 2933 (NeH), 1665 (C]O),
1531, 1166, 1078, 862, 645 cmꢀ1; 1H NMR (CDCl3, 300 MHz):
d
1.28
(s, 3H, CH3), 1.36 (d, 3H, 3JH,H ¼ 6.8 Hz, alaCH3), 1.43 (s, 3H, CH3), 1.44
(s, 9H, BocCH3), 3.15e3.23 (m, 1H, H-5), 3.46 (s, 1H, OH), 3.75e3.81
(m, 2H, H-3 and H-5), 3.91e3.97 (m, 1H, BocNHCH), 4.49 (d,
3JH,H ¼ 3.8 Hz, 1H, H-2), 4.63 (d, 3JH,H ¼ 3.0 Hz, 1H, BocNH), 4.84 (dd,
3JH,H ¼ 7.6 Hz and 1.6 Hz, 1H, H-4), 5.82 (d, 3JH,H ¼ 3.8 Hz, 1H, H-1),
5-(N-Boc-L-phenylalaninlyamido)-5-deoxy-1,2-O-isopropylidene-
a
-D-xylofuranose (3f)
24
White solid; yield: 0.38 g (86%); mp: 135e140 ꢂC; [
a]
¼ þ35.8
6.75 (m, 1H, NH) ppm; 13C NMR (CDCl3, 75.5 MHz): 17.96 (alaCH3),
d
D
26.20 (CH3), 26.91 (CH3), 28.41 (BocCH3), 37.21 (alaCH), 50.10 (C-5),
73.78 (C-2), 79.95 (C-3), 80.56 (BocC(CH3)3), 84.86 (C-4), 104.86 (C-
1), 111.40 (C(CH3)2), 155.59 (BocCO), 174.78 (NHCO) ppm; Anal. calcd.
for C16H28N2O7: C, 53.32; H, 7.83; N, 7.77%; found: C, 53.19; H, 7.51;
N, 7.58%; MS (ESIþ): m/z ¼ 361 [M þ H]þ.
(CHCl3, c 0.1); IR (KBr, ymax): 3429, 3351, 2983, 2932 (NeH), 1665
(C]O), 1523, 1168, 1007, 858, 592 cmꢀ1; 1H NMR (CDCl3, 300 MHz):
d
1.28 (s, 3H, CH3), 1.41 (s, 9H, BocCH3), 1.49 (s, 3H, CH3), 3.02e3.10
(m, 3H, H-5 and ArCH2), 3.63e3.74 (m, 1H, H-5), 3.85e3.90 (m, 2H,
3
H-3 and OH), 4.21e4.28 (m, 1H, BocNHCH), 4.48 (d, JH,H ¼ 3.4 Hz,
1H, H-2), 4.67 (d, 3JH,H ¼ 2.0 Hz, 1H, BocNH), 4.97 (m, 1H, H-4), 5.79
3
(d, JH,H ¼ 3.4 Hz, 1H, H-1), 6.39 (bs, 1H, BocNH), 7.15 (m, 2H, Ar),
5-(N-Boc-L-valinlyamido)-5-deoxy-1,2-O-isopropylidene-a-D-
7.25e7.31 (m, 3H, Ar) ppm; 13C NMR (CDCl3, 75.5 MHz):
d 26.17
xylofuranose (3c)
24
(CH3), 26.84 (CH3), 28.33 (BocCH3), 37.21 (phealaCH2), 38.45 (phea-
laCH), 55.97 (C-5), 73.74 (C-2), 79.67 (C-3), 80.39 (BocC(CH3)3), 84.85
(C-4), 104.77 (C-1), 111.35 (C(CH3)2), 127.11 (Ar), 128.71 (Ar), 129.24
(Ar), 136.32 (Ar), 155.40 (BocCO), 173.34 (NHCO), ppm; Anal. calcd.
for C22H32N2O7: C, 60.54; H, 7.39; N, 6.42%; found C, 60.19; H, 7.05;
N, 6.14%; MS (ESIþ): m/z ¼ 437 [M þ H]þ.
White solid; yield: 0.36 g (92%); mp: 130e135 ꢂC; [
a
]
¼ þ16.93
D
(CHCl3, c 0.1); IR (KBr, ymax): 3397, 3341, 2984, 2929 (NeH), 1657
(C]O), 1528, 1166, 1015, 861, 638 cmꢀ1; 1H NMR (CDCl3, 400 MHz):
3
d
0.95 (dd, JH,H ¼ 6.4 Hz and 8.9 Hz, 6H, valCH3), 1.29 (s, 3H, CH3),
1.44 (s, 3H, CH3), 1.45 (s, 9H, BocCH3), 1.51e1.53 (m, 1H, valCH),
3.19e3.23 (m, 1H, H-5), 3.75e3.82 (m, 2H, H-5 and H-3), 3.88 (s, 1H,
OH), 3.96e3.98 (m,1H, BocNHCH), 4.51 (d, JH,H ¼ 3.9 Hz, 1H, H-2),
3
4.72 (bs, 1H, BocNH), 4.97 (dd, JH,H ¼ 7.9 Hz and 1.0 Hz, 1H, H-4),
3
General procedure for the synthesis of ferrocenyl pseudo-dipeptides
(5aef)
5.84 (d, JH,H ¼ 3.9 Hz, 1H, H-1), 6.71 (m, 1H, NH) ppm; 13C NMR
3
(CDCl3, 75.5 MHz): d
17.86 (valCH3),19.31 (valCH3), 26.09 (CH3), 26.82
(CH3), 28.27 (BocCH3), 30.22 (valCH), 37.11 (valCH), 60.3 (C-5), 73.77
(C-2), 79.85 (C-3), 80.55 (BocC(CH3)3), 84.80 (C-4), 104.81 (C-1),
111.53 (C(CH3)2), 161.11 (BocCO), 174.16 (NHCO) ppm; Anal. calcd. for
The selective N-Boc deprotection of the pseudo-dipeptides
(3aef) (1 mmol) was carried out by reacting them with a TFA-
CH2Cl2 mixture (50% v/v, 4 mL). The stirring was continued till the
disappearance of the starting material (approximately 4 h) and the
solvent was evaporated to dryness. The resulting residue was dis-
solved in CH2Cl2 and cooled in an ice bath. To this solution, Et3N
(1 mmol) was added drop wise and the resulting solution was
stirred at 0 ꢂC for 30 min. At this temperature, a solution of ferro-
cenoyl chloride (approx. 1 mmol) in CH2Cl2 and Et3N (1.5 mmol)
were added. The reaction mixture was allowed to attain room
temperature and the stirring was continued for 12 h. The reaction
mixture was quenched with saturated NaHCO3 solution and
extracted with CH2Cl2. After drying over anhydrous NaSO4, the
combined organic layers were evaporated to dryness and the crude
compound was purified by silica gel column chromatography using
hexane and ethyl acetate mixture.
C
18H32N2O7: C, 55.65; H, 8.30; N, 7.21%; found: C, 55.49; H, 8.19; N,
7.15%; MS (ESIþ): m/z ¼ 389 [M þ H]þ.
5-(N-Boc-L-leucinlyamido)-5-deoxy-1,2-O-isopropylidene-a-D-
xylofuranose (3d)
24
White solid; yield: 0.35 g (87%); mp: 120e125 ꢂC; [
a]
¼ ꢀ12.97
D
(CHCl3, c 0.1); IR (KBr, ymax): 3363, 2979, 2927 (NeH), 1661 (C]O),
1522, 1169, 1011, 860, 650 cmꢀ1; 1H NMR (CDCl3, 300 MHz):
d
0.94
(dd, 6H, 3JH,H ¼ 3.8 Hz and 2.3 Hz, leuCH3), 1.28 (s, 3H, CH3), 1.40 (s,
12H, BocCH3 and CH3),1.61e1.68 (m, 3H, leuCH2 and leuCH), 3.15e3.22
(m, 1H, H-5), 3.46 (s, 1H, OH), 3.70e3.80 (m, 1H, H-5), 3.81e3.84 (d,
3JH,H ¼ 2.3 Hz, 1H, BocNHCH), 3.91e4.01 (m, 1H, H-3), 4.49 (d, 1H,
3JH,H ¼ 3.0 Hz, H-2), 4.68 (bs, 1H, BocNH), 4.77 (m, 1H, H-4), 5.82 (d,
1H, 3JH,H ¼ 3.0 Hz, H-1), 6.71 (bs, 1H, CONH) ppm; 13C NMR (CDCl3,
75.5 MHz):
d
21.86 (leuCH3), 22.86 (leuCH3), 24.72 (leuCH2), 26.07
(CH3), 26.77 (CH3), 28.25 (BocCH3), 37.03 (leuCH), 40.57 (leuCH3),
53.17 (C-5), 73.66 (C-2), 79.89 (C-3), 80.65 ((BocC(CH3)3), 84.71 (C-
4), 104.80 (C-1), 111.47 (C(CH3)2), 155.83 (BocCO), 175.04 (NHCO)
ppm; Anal. calcd. for C19H34N2O7: C, 56.70; H, 8.51; N, 6.96%; found:
C, 56.58; H, 8.27; N, 6.38%; MS (ESIþ): m/z ¼ 403 [M þ H]þ.
5-(N-ferrocenoyl-L-glycinylamido)-5-deoxy-1,2-O-isopropylidene-
a
-D-xylofuranose (5a)
Orange solid; yield: 0.29 g (63%); m. p.: 75 ꢂC; [
a
]
D
24: þ30.12
(CH3OH, c 0.1); IR (KBr, ymax): 3423, 2932 (NeH), 1634 (C]O), 1544,
1379, 1163, 1074, 822, 627 cmꢀ1; 1H NMR (CDCl3, 300 MHz):
d 1.30
(s, 3H, CH3), 1.47 (s, 3H, CH3), 3.30e3.40 (m, 2H, H-5), 3.76e3.80 (m,
1H, H-3), 4.06e4.08 (m, 3H, GlyCH2, OH), 4.11e4.17 (m,1H, H-4), 4.22
(s, 5H, C5H5), 4.34 (dd, J ¼ 1.6 and 1.4 Hz, 2H, C5H4), 4.57 (d,
J ¼ 3.1 Hz, H-2), 4.71 (dd, J ¼ 1.6 Hz and 1.4 Hz, 2H, C5H4), 5.91 (d,
J ¼ 3.1 Hz, H-1), 6.64 (m, 1H, NH), 7.10e7.13 (m, 1H, NH) ppm; 13C
5-(N-Boc-L-isoleucinlyamido)-5-deoxy-1,2-O-isopropylidene-
a-D-
xylofuranose (3e)
24
White solid; yield: 0.34 g (84%); mp: 135e140 ꢂC; [
a]
¼ þ22.13
D
(CHCl3, c 0.1); IR (KBr, ymax): 3356, 2978, 2930 (NeH), 1663 (C]O),
1522, 1169, 1016, 856, 650 cmꢀ1 1H NMR (CDCl3, 400 MHz):
;
NMR (CDCl3, 75.5 MHz): d 26.09 (CH3), 26.80 (CH3), 37.42 (CH2),
d
0.92e0.95 (m, 6H, isoleuCH3), 1.08e1.17 (m, 2H, isolueCH2), 1.29 (s,
43.52 (C-5), 68.25, 68.31, 69.88, 71.03 (Cp), 73.94 (C-2), 79.50 (C-3),
84.81 (C-4), 104.80 (C-1), 111.59 (C(CH3)2), 171.36 (CO), 171.97 (CO),
ppm; Anal. calcd for C21H26FeN2O6: C, 55.04; H, 5.72; N, 6.11%;
found C, 54. 79; H, 5.43; N 5.81%; MS (ESIþ): m/z ¼ 481 [M þ Na]þ.
3H, CH3), 1.45 (s, 12H, BocCH3 and CH3), 1.87e1.97 (m, 1H, isoleuCH),
3.18e3.23 (m, 1H, H-5), 3.71e3.85 (m, 2H, H-5 and H-3), 3.87 (s, 1H,
OH), 3.96e3.99 (m, 1H, BocNHCH), 4.51 (d, JH,H ¼ 2.9 Hz, 1H, H-2),
3