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J. G. Knight, K. Tchabanenko / Tetrahedron 58 (2002) 6659–6664
4.2.1. (4S,5SR )-4-Benzyl-5-(hex-1-ynyl)oxazolidin-2-one
8a. Hex-1-ynyllithium addition to N-Boc-phenylalaninal
(1.25 g, 5 mmol) gave a mixture of diastereoisomeric
oxazolidinones 8a (758 mg, 59%) (anti/syn, 3:1); pale
yellow oil; nmax (cm21) (film) 3274 (br), 1756 (s), 1382 (m),
1336 (m), 1232 (s), 995 (s), 701 (s); dH (500 MHz, CDCl3)
7.24–7.03 (5H, m, major and minor), 5.62 (1H, br s, major),
5.22 (1H, br s, minor), 5.20 (1H, dt, J¼7.5 Hz, 1.5, minor),
4.72 (1H, dt, J¼6.0, 1.0 Hz, major), 3.93–3.83 (1H, m,
major and minor), 2.97 (1H, dd, J¼13.5, 4.0 Hz, minor),
2.83 (1H, dd, J¼14.0, 5.5 Hz, major), 2.74 (1H, dd, J¼13.5,
10.0 Hz, minor), 2.68 (1H, dd, J¼14.0, 8.5 Hz, major), 2.18
(2H, dt, J¼7.0, 1.5 Hz, minor), 2.07 (2H, dt, J¼7.0, 1.0 Hz,
major), 1.45–1.19 (4H, m, major and minor), 0.77 (3H, t,
J¼6.0 Hz, minor), 0.76 (3H, t, J¼7.5 Hz, major); dC
(125 MHz, CDCl3) (major and minor) 157.8, 157.6, 136.6,
135.6, 129.3, 129.1, 128.9, 128.5, 127.3, 127.1, 92.4, 89.9,
75.1, 72.5, 71.1, 70.4, 61.0, 56.5, 40.5, 38.3, 30.2, 30.1,
21.9, 21.8, 18.4, 18.3, 14.1, 13.5; m/z (EIþ) 257 (Mþ, 20%),
196 (42), 166 (87), 91 (100); Found (Mþ) 257.1406,
C16H19NO2 requires 257.1415.
5.11 (1H, br s), 3.93 (1H, ddd, J¼11.0, 9.0, 3.5 Hz), 2.74
(1H, dd, J¼14.0, 3.5 Hz), 2.74 (1H, dd, J¼14.0, 11.0 Hz),
2.12–2.07 (1H, m), 2.02–1.94 (1H, m), 1.35–1.22 (4H, m),
0.85 (3H, t, J¼7.5 Hz); dC (125 MHz, CDCl3) 158.6, 137.4,
136.8, 129.0, 128.9, 127.1, 122.4, 75.6, 57.3, 37.2, 31.4,
27.6, 22.2, 13.8; m/z (EIþ) 259 (Mþ, 55%), 177 (62), 167
(78), 124 (53), 91 (100); Found (Mþ) 259.1564, C16H21NO2
requires 259.1572; and (4S,5S)-4-benzyl-5-((Z)hex-1-enyl)-
oxazolidin-2-one 4a: (335 mg, 68%) as a colorless oil;
[a ]2D1¼22.4 (c¼0.6, CHCl3); nmax (cm21) (film) 3291 (br),
1751 (s), 1456 (m), 1386 (m), 998 (m); dH (500 MHz,
CDCl3) 7.28–7.09 (5H, m), 5.63 (1H, dt, J¼11.0, 7.5 Hz),
5.42 (1H, ddt, J¼11.0, 9.0, 1.5 Hz), 5.19 (1H, br s), 4.95
(1H, dd, J¼9.0, 6.5 Hz), 3.66 (1H, ddd, J¼8.5, 6.5, 5.0 Hz),
2.83 (1H, dd, J¼13.5, 5.0 Hz), 2.74 (1H, dd, J¼13.5,
8.5 Hz), 2.03–1.95 (1H, m), 1.92–1.84 (1H, m), 1.27–1.09
(4H, m), 0.81 (3H, t, J¼7.0 Hz); dC (125 MHz, CDCl3)
158.5, 137.4, 136.1, 129.0, 128.9, 127.2, 125.2, 77.4, 60.3,
40.6, 31.6, 27.4, 22.2, 13.9; m/z (EIþ) 259 (Mþ, 55%), 177
(62), 167 (78), 124 (53), 91 (100); Found (Mþ) 259.1564,
C16H21NO2 requires 259.1572.
4.2.2. (4S,5SR )-4-Benzyl-5-(3-phenylprop-1-ynyl)oxa-
zolidin-2-one 8b. 3-Phenylprop-1-ynyllithium addition to
N-Boc-phenylalaninal (1.25 g, 5 mmol) gave a mixture of
diastereoisomeric oxazolidinones 8b (902 mg, 62%) (anti/
syn, 3:2) as a colorless oil; nmax (cm21) (film) 3276 (br s),
1741 (s), 1494 (m), 1384 (m),1232 (m), 1029 (s), 745 (s),
700 (s); dH (500 MHz, CDCl3) 7.24–7.04 (10H, m, major
and minor), 6.42 (1H, br s, major), 5.9 (1H, br s, minor),
5.22 (1H, dt, J¼9.5, 2.0 Hz, minor), 4.78 (1H, dt, J¼6.0,
2.0 Hz, major), 3.98–3.86 (1H, m, major and minor), 3.49
(2H, d, J¼2.0 Hz, minor), 3.48 (2H, d, J¼2.0 Hz, major),
2.99 (1H, dd, J¼14.0, 5.0 Hz, minor), 2.80 (1H, dd, J¼14.0,
9.0 Hz, minor), 2.77 (2H, dd, J¼6.5, 5.0 Hz, major); dC
(125 MHz, CDCl3) (major and minor) 158.1, 157.9, 136.4,
135.3, 135.2, 135.1, 129.0, 128.9, 128.8, 128.7, 128.5,
128.4, 127.7, 127.6, 127.0, 126.9, 126.7, 126.6, 89.5, 86.8,
77.3, 74.7, 70.6, 70.5, 70.2, 70.1, 60.6, 56.4, 40.2, 38.1; m/z
(EIþ) 291 (Mþ, 10%), 230 (25), 200 (55), 156 (47), 129
(60), 91 (100); Found (Mþ) 291.1266, C19H17NO2 requires
291.1259.
4.3.2. (4S,5R )-4-Benzyl-5-(3-phenyl(Z )prop-1-enyl)oxa-
zolidin-2-one 3b. Following the Lindlar reduction pro-
cedure, butynyloxazolidinones 8b (450 mg, 1.55 mmol)
gave: the vinyloxazolidinone 3b (159 mg, 35%) as white
needles; mp 95–988C; [a ]2D1¼þ2.8 (c¼0.4, CHCl3); nmax
(cm21) (KBr) 3276 (br s), 1741 (s), 1494 (m), 1384
(m),1232 (m), 1029 (s), 745 (s), 700 (s); dH (500 MHz,
CDCl3) 7.25–7.02 (10H, m), 5.97 (1H, dtd, J¼10.0, 7.5,
1.0 Hz), 5.72 (1H, ddd, J¼10.0, 9.0, 2.0 Hz), 5.48 (1H, ddd,
J¼9.0, 8.0, 1.0 Hz), 5.04 (1H, br s), 3.87 (1H, ddd, J¼11.0,
8.0, 3.5 Hz), 3.47 (1H, dd, J¼15.5, 7.5 Hz), 3.31 (1H, ddd,
J¼15.5, 7.5, 2.0 Hz), 2.69 (1H, dd, J¼13.5, 3.5 Hz), 2.57
(1H, dd, J¼13.5, 8.0 Hz); dC (125 MHz, CDCl3) 158.4,
139.1, 136.7, 135.2, 129.0, 128.9, 128.7, 128.3, 127.1,
126.5, 123.7; 75.5, 57.3, 37.3, 33.9; m/z (EIþ) 293 (Mþ,
18%), 281 (20), 265 (40), 231 (55), 202 (95), 158 (75), 91
(100); Found (Mþ) 293.1403, C19H19NO2 requires
293.1415; and (4S,5S)-4-benzyl-5-(3-phenyl(Z)prop-1-
enyl)oxazolidin-2-one 4b: (236 mg, 52%) as a colorless
oil; [a]2D1¼þ3.5 (c¼0.7, CHCl3); nmax (cm21) (film) 3276
(br s), 1741 (s), 1494 (m), 1384 (m),1232 (m), 1029 (s), 745
(s), 700 (s); dH (500 MHz, CDCl3) 7.23–6.93 (10H, m),
6.33 (1H, br s), 5.7 (1H, dt, J¼10.0, 8.0 Hz), 5.49 (1H, ddt,
J¼10.0, 9.0, 1.5 Hz), 5.01 (1H, dd, J¼9.0, 5.5 Hz), 3.70
(1H, td, J¼6.5, 5.5 Hz), 3.24 (1H, dd, J¼15.5, 8.0 Hz), 3.07
(1H, dd, J¼15.5, 8.0 Hz), 2.79 (1H, dd, J¼6.5, 13.5 Hz),
2.72 (1H, dd, J¼6.5, 13.5 Hz); dC (125 MHz, CDCl3) 159.1,
139.2, 136.7, 134.8, 129.1, 128.8, 128.7, 128.5, 128.4, 127.1,
126.5, 75.5, 60.1, 40.6, 33.5; m/z (EIþ) 293 (Mþ, 18%), 281
(20), 265 (40), 231 (55), 202 (95), 158 (75), 91 (100); Found
(Mþ) 293.1403, C19H19NO2 requires 293.1415.
4.3. General procedure for synthesis of Z-vinyl-
oxazolidinones (Lindlar reduction)
To a solution of alkynyl oxazolidinone 8 (1 mmol) and
quinoline (100 ml, 0.008 mmol) in MeOH (50 ml) was
added Lindlar catalyst (100 mg). The flask was flushed with
H2 and the reaction was stirred for 3 h under H2 (1 atm) at
ambient temperature. The mixture was then filtered through
Celite, the combined filtrates were evaporated and the
residue was purified by chromatography (petrol/EtOAc, 3:1)
to give the syn and anti Z-vinyl oxazolidinones.
4.3.3. (4S,5R)-4-Benzyl-5-(E-1-hexenyl)oxazolidin-2-one
5a and (4S,5S )-4-benzyl-5-(E-1-hexenyl)oxazolidin-2-
one 6a. To a stirred solution of (E)-1-iodo-1-hexene
(3.15 g, 15 mmol) in THF (60 ml) was added n-BuLi
(7.4 ml, 2.0 M solution in hexanes, 14.8 mmol) dropwise
at 2788C. Stirring was continued for an additional 15 min
and a solution of N-Boc-phenylalaninal (1.25 g, 5 mmol) in
THF (20 ml) was added dropwise. The resulting solution
was stirred for 3 h at 2788C, allowed to warm to 08C, stirred
4.3.1. (4S,5R )-4-Benzyl-5-((Z )hex-1-enyl)oxazolidin-2-
one 3a. Following the Lindlar reduction procedure,
butynyloxazolidinones 8a (500 mg, 1.9 mmol) gave: the
vinyloxazolidinone 3a (112 mg, 23%) as a colorless oil;
[a ]2D1¼226.5 (c¼0.7, CHCl3); nmax (cm21) (film) 3291
(br), 1751 (s), 1456 (m), 1386 (m), 998 (m); dH (500 MHz,
CDCl3) 7.28–7.04 (5H, m), 5.75 (1H, dt, J¼11.0, 8.0 Hz),
5.56 (1H, dd, J¼11.0, 9.5 Hz), 5.40 (1H, dd, J¼9.5, 9.0 Hz),