J = 8 Hz, 6H, CH(CH3)2); 13C NMR (125 MHz, CDCl3): d 202.48,
166.89, 156.15, 136.16, 128.59, 128.28, 128.11, 67.16, 61.60, 58.60,
46.41, 39.98, 24.81, 23.29, 21.54, 14.09; MALDI TOF/TOF m/z
Calcd. for C18H25NO5 [M+K]+ 374.1370, obsrvd. 374.1369.
3.55–3.45 (dd, J = 15.6 Hz, J = 9.16 Hz, 2H, CH2, AB coupling),
3.12–3.02 (q, J = 7.3 Hz, 2H, CH2NH–Boc), 1.95–1.84 (m, 2H,
CH2), 1.71–1.41 (m, 4H,–CH2 CH2–), 1.37 (s, 9H, C(CH3)3, Boc),
1.27–1.23 (t, J = 7.1 Hz, 3H, CH3); 13C NMR (100 MHz, CDCl3):
d 201.96, 166.89, 156.27, 143.80, 141.41, 127.84, 127.18, 125.12,
120.09, 79.34, 67.00, 61.74, 60.01, 47.28, 46.27, 39.86, 30.34, 29.78,
28.50, 22.19, 14.18; HR-MS m/z Calcd. for C30H38N2O7 [M+Na]+
561.2576, obsrvd. 561.2577.
(S)-1-benzyl 6-ethyl 2-(benzylcarbonylamino)-4-oxohexanedioate
(4j)
◦
White solid (0.589 g, 69%); melting point = 68.3 C; [a]D25
=
1
-16.30 (c = 1, MeOH); H NMR (400 MHz, CDCl3): d 12.06
(s, 1H, enolic), 7.33–7.28 (m, 10H, aromatic), 5.75–5.72 (d,
J = 8.2 Hz, 1H, NH), 5.63–5.59 (m, 1H, CH), 5.14 (s, 2H, –
OCH2Ph), 5.08 (s, 2H, –OCH2Ph), 4.17–4.11 (q, J = 7 Hz, 2H,
–OCH2Me), 3.39 (s, 2H, CH2, AB coupling), 3.33–3.10 (m, 2H,
CH2), 1.24–1.21 (t, J = 7.1 Hz, 3H, CH3); 13C NMR (100 MHz,
CDCl3): d 200.78, 170.51, 166.42,155.99, 136.02, 135.10, 128.57,
128.50,128.42, 128.21, 128.03, 67.57, 67.08, 61.59, 49.88, 49.07,
44.59, 14.01; MALDI TOF/TOF m/z Calcd. for C23H25NO7
[M+K]+ 466.1268, obsrvd. 466.1276.
(S)-ethyl 4-(((9H-fluoren-9-yl)methoxy)carbonylamino)-5-(4-tert-
butoxyphenyl)-3-oxopentanoate (4n)
Colorless gummy (0.88 g, 83.3%); [a]2D5 = -37.45 (c = 1, MeOH);
1H NMR (400 MHz, CDCl3): d 12.17 (s, 1H, enolic), 7.75–7.28
(m, 8H, aromatic, Fmoc-), 7.03–7.01 (d, J = 8.3 Hz, 2H, aromatic,
Ph–), 6.90–6.88 (d, J = 8.3 Hz, 2H, aromatic, Ph–), 5.33–5.31 (d,
J = 7.8 Hz, 1H, NH), 4.64–4.587 (m, 1H, CH), 4.39–4.38 (d, J =
6.9 Hz, 2H, CH2), 4.19–4.10 (m, 3H, –OCH2, CH–Fmoc), 3.44–
3.34 (dd, J = 16 Hz, J = 11.4 Hz, 2H, CH2, AB coupling), 3.09–2.94
(m, 2H, –CH2Ph–OtBu), 1.30 (s, 9H, –C(CH3)3, OtBu), 1.25–1.22
(t, J = 7.1 Hz, 3H, CH3); 13C NMR (100 MHz, CDCl3): d 201.5121,
166.6250, 155.6698,154.4971, 143.6181, 141.2917, 130.39, 129.69,
127.73, 1.27.68, 127.04, 124.97, 124.36,124.24, 124.19, 119.97,
78.87, 66.90, 61.54, 60.81, 47.14, 46.97, 36.43, 28.77, 14.04;
HR-MS m/z Calcd. for C32H35NO6 [M+Na]+ 552.2362, obsrvd.
552.2363.
(S)-ethyl 4-(((9H-fluoren-9-yl)mehtoxy)carbonylamino)-6-methyl-
3-oxoheptanoate (4k)
1
Colorless liquid (0.651 g, 77%); [a]2D5 = -28.9 (c = 1, MeOH); H
NMR (500 MHz, CDCl3): d 12.16 (s, 1H, enolic), 7.80–7.79 (d,
J = 7.5 Hz, 2H, aromatic, Fmoc-), 7.63–7.61 (t, J = 6.5 Hz, 2H,
aromatic, Fmoc-), 7.44–7.42 (t, J = 7.5 Hz, 2H, aromatic, Fmoc-),
7.36–7.33 (t, J = 7.5 Hz, 2H, aromatic, Fmoc-), 5.26–5.24 (d, J =
8 Hz, 1H, NH), 4.50–4.45 (m, 3H, CH, CH2), 4.26–4.21 (m, 3H,–
OCH2, CH-Fmoc), 3.59–3.50 (dd, J = 16 Hz, J = 13 Hz, 2H, CH2,
AB coupling), 1.71–1.68 (m, 2H, CH2), 1.47–1.43 (m, 1H, CH),
1.34–1.30 (t, J = 7 Hz, 3H, CH3), 1.00–0.97 (m, 6H, C(CH3)2);
13C NMR (125 MHz, CDCl3): d 202.54, 166.91, 156.13, 143.72,
141.38, 127.78, 127.11, 125.08, 120.05, 66.87, 61.63, 58.56, 47.28,
46.35, 39.93, 24.80, 23.33, 21.54, 14.13; MALDI TOF/TOF m/z
Calcd. for C25H29NO5 [M+K] + 462.1683, obsrvd. 462.1631.
Acknowledgements
We gratefully acknowledge Indian Institute of Science Education
and Research, Pune (IISER-P) for financial support and A. B, S.
M. M and S.V. J are thankful to CSIR, Govt. of India for Junior
Research fellowship. We thank NCL, Pune and Department of
Organic Chemistry, IISc, Bangalore for LC-MS and HRMS,
respectively.
References
(S)-1-tert-butyl 6-ethyl 3-(((9H-fluoren-9-yl)methoxy)-
carbonylamino)-4-oxohexanedioate (4l)
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Colorless liquid (0.742 g, 77.2%); [a]2D5 = 1.43 (c = 1, MeOH);
1H NMR (500 MHz, CDCl3): d 12.11 (s, 1H, enolic 5.5%), 7.78–
7.32 (m, 8H, aromatic, Fmoc), 5.91 (b, s, 1H, NH), 4.60–4.51
(m, 2H, CH2), 4.45–4.41 (m, 1H, CH), 4.24–4.18 (m, 3H,–OCH2,
CH–Fmoc), 3.56 (s, 2H, aCH2), 2.94–2.69 (dd, J = 16.5 Hz, J =
t
13.8 Hz, 2H, –CH2CO2 Bu), 1.44 (s, 9H, –OC(CH3)3), 1.28–1.25 (t,
J = 7.3 Hz, CH3); 13C NMR (125 MHz, CDCl3): d 201.05, 170.52,
166.87, 156.00, 143.67, 141.39, 127.83, 127.11, 125.08, 120.09,
82.17, 67.13, 61.57, 56.70, 47.23, 46.03, 36.57, 28.035, 14.10;
HR-MS m/z Calcd. for C27H31NO7 [M+K]+ 520.1738, obsrvd.
520.1722.
(S)-ethyl 4-(((9H-fluoren-9-yl) mehtoxy)carbonylamino)-8-(tert-
butoxycarbonylamino)-3-oxooctanoate (4m)
◦
White solid (0.862 g, 80.2%); melting point = 114 C; [a]D25
=
-81.53(c = 1, MeOH); 1H NMR (400 MHz, CDCl3): d 12.11
(s, 1H, enolic), 7.760–7.28 (m, 8H, aromatic, Fmoc-), 5.57–5.56
(d, J = 7.3 Hz, 1H, NH–Fmoc), 4.59 (s, b,1H, NH-Boc), 4.45–
4.39 (m, 3H, CH, CH2), 4.21–4.16 (m, 3H, –OCH2, CH–Fmoc),
This journal is
The Royal Society of Chemistry 2010
Org. Biomol. Chem., 2010, 8, 4855–4860 | 4859
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