2688
N. Baig. R.B.
LETTER
1H NMR (300 MHz, CDCl3): d = 7.27 (s, 5 H), 4.09 (s, 2 H),
2.31 (s, 3 H). 13C (75 MHz, CDCl3): d = 194.8, 137.4, 128.6,
128.4, 127.1, 33.2, 30.1. HRMS: m/z calcd for C9H10OS:
189.030 [M + Na]; found: 189.0358.
171.8,169.6, 156.3, 136.0, 128.4, 128.1, 128.0, 67.7, 56.6,
55.0, 52.1, 37.6, 31.4, 30.4, 25.0, 15.3, 11.2. HRMS: m/z
calcd for C20H28N2O8S: 447.1506 [M + Na]; found:
447.1563.
Compound 4d: oily liquid, yield 96%. IR: 2988 (w), 1676
(s), 1416 (m), 1176 (s), 625 (m) cm–1. 1H NMR (300 MHz,
CDCl3): d = 7.88 (d, J = 8.1 Hz, 2 H), 7.30 (d, J = 8.1 Hz,
2 H), 4.13 (s, 2 H), 2.57 (s, 3 H), 2.35 (s, 3 H). 13C NMR (75
MHz, CDCl3): d = 197.4, 194.5.
Compound 4l: oily liquid, yield 80%. IR (neat): 2903 (m),
2863 (w), 1732 (s), 1462 (m), 1110 (s) cm–1. 1H NMR (300
MHz, CDCl3): d = 2.71 (m, 1 H), 2.37 (s, 3 H), 1.70–1.30 (m,
8 H), 1.00 (t, J = 7.2 Hz, 3 H), 0.91 (t, J = 7.2 Hz, 3 H).
13C NMR (75 MHz, CDCl3): d = 195.4, 54.4, 33.0, 26.7,
22.5, 13.8, 11.0. HRMS: m/z calcd for C9H18OS: 197.0976
[M + Na]; found: 197.0970.
(24) To a solution of dipeptide 9 (1.0 mmol, 0.366 g) and pyridine
(5 mmol, 0.395 g) in CH2Cl2 (10 mL) at –10 °C MsCl (1.2
mmol, 0.136 g) was added and the reaction mixture was
stirred for 6 h. The reaction was quenched with H2O and
extracted with CH2Cl2 (3 × 15 mL). The organic extract was
washed with brine, dried over Na2SO4, and concentrated.
The crude product was purified by column chromatography
on silica gel (100–200 mesh), white solid, mp 119 °C, yield
95%; [a]D28 +15.7 (c 1, CHCl3). IR (neat): 3334 (br), 2964
(m), 1731 (s), 1674 (s), 1529 (m), 1361 (m), 1170 (m) cm–1.
1H NMR (300 MHz, CDCl3): d = 7.31 (s, 5 H), 6.95 (d,
J = 7.5 Hz, 1 H), 5.68 (d, J = 7.2 Hz, 1 H), 5.14 (s, 2 H),
4.61–4.53 (m, 3 H), 4.35 (dd, J = 9.0, 7.2 Hz, 1 H), 3.80 (s,
3 H), 3.00 (s, 3 H), 1.93–1.84 (m, 1 H), 1.45–1.33 (m, 1 H),
1.25–1.00 (m, 1 H), 0.92–0.86 (m, 6 H). 13C NMR (100
MHz, CDCl3): d = 171.7, 167.7, 155.9, 135.6, 128.54, 128.3,
128.1, 68.3, 67.5, 56.7, 53.6, 52.2, 37.6, 37.2, 24.9, 15.3,
11.4. HRMS: m/z calcd for C19H28N2O8S: 467.1467 [M +
Na]; found: 467.1451.
(25) Compound 11 was obtained in optically pure form and there
was no racemization or formation of diastereomer.
(26) Pachamuthu, K.; Schmidt, R. R. Chem. Rev. 2006, 106, 160.
(27) Blank-Muesser, M.; Defaye, J.; Driguez, H. J. Chem. Soc.,
Perkin Trans. 1 1982, 15.
(28) Zhichao, P.; Hai, D.; Remi, C.; Olof, R. Eur. J. Org. Chem.
2007, 4927.
(29) Ibatullin, M. F.; Shabalin, A. K.; Janis, V. J.; Shavva, G. A.
Tetrahedron Lett. 2003, 44, 7961; and references cited
therein.
Compound 8: white solid, mp 77 °C, yield 80%; [a]D28 –48
(c 1, CHCl3). IR (neat): 3351 (br), 2951 (w), 1698 (s), 1517
(m), 1212 (m) cm–1. 1H NMR (400 MHz, CDCl3): d = 7.33
(m, 5 H), 5.55 (d, J = 7.2 Hz, 1 H), 5.11 (s, 2 H), 4.50–4.60
(m, 1 H), 3.75 (s, 3 H), 3.42 (dd, J = 14.0, 4.8 Hz, 1 H), 3.40
(dd, J = 14.0, 4.8 Hz, 1 H), 2.32 (s, 3 H). 13C NMR (100
MHz, CDCl3): d = 194.8, 170.5, 155.6, 136.0, 128.4, 128.1,
128.0, 67.0, 53.4, 52.7, 31.1, 30.3. HRMS: m/z calcd for
C14H17O5S: 334.0725 [M + Na]; found 334.0710.
Compound 11: gummy solid, yield 78%; [a]D28 +8.7 (c 1,
CHCl3). IR (neat): 3318 (br), 2965 (m), 2930 (m), 1736 (s),
1695 (s), 1682 (s), 1635 (m), 1262 (m), 1213 (m), 1139 (m)
cm–1. 1H NMR (400 MHz, CDCl3): d = 7.34 (s, 5 H), 6.92 (d,
J = 8.0 Hz, 1 H), 5.67 (d, J = 8.0 Hz, 1 H), 5.12 (s, 2 H), 4.52
(dd, J = 8.6, 4.8 Hz 1 H), 4.40 (m, 1 H), 3.35 (dd, J = 16.0,
4.0 Hz, 1 H), 3.12 (dd, J = 16.0, 8.0 Hz, 1 H), 2.30 (s, 3 H),
1.90–1.86 (m, 1 H), 1.44–1.36 (m, 1 H), 1.18–1.12 (m, 1 H),
0.90–0.86 (m, 6 H). 13C NMR (100 MHz, CDCl3): d = 196.6,
Synlett 2008, No. 17, 2684–2688 © Thieme Stuttgart · New York