158
P. Scafato et al. / Tetrahedron 58 )2002) 153±159
brine and dried over Na2SO4. After evaporation of solvent
the residue was puri®ed by column chromatography on
silica gel.
+300 MHz, CDCl3) d 4.37 +d, J11.9 Hz, 1H), 4.59 +d,
J11.9 Hz, 1H), 4.74 +d, J8.0 Hz, 1H), 6.32 +d,
J8.0 Hz, 1H), 7.16±7.59 +m, 22H), 7.94 +d, J7.7 Hz,
2H); 13C NMR +75 MHz, CDCl3) d 70.4, 80.4, 83.7,
127.1, 127.2, 127.7, 127.9, 128.0, 128.2, 128.3, 128.4,
128.7, 130.1, 132.4, 134.7, 135.8, 136.9, 140.4, 140.9,
163.3, 186.5.
3.5.1. ꢀ1R,2R)-1,2-Diphenyl-2-ꢀ4-tri¯uoromethylbenzyl-
oxy)-ethylphenylglyoxylate ꢀ3b). The residue was puri®ed
by column chromatography +petroleum ether/Et2O 4:1),
obtaining 3b as a yellow viscous liquid, in 99% yield.
[Found: C, 71.7; H, 4.3. C30H23F3O4 requires C, 71.42; H,
3.5.5. ꢀ1R,2R)-1,2-Diphenyl-2-ꢀ2,3,4,5,6-penta¯uoroben-
zyloxy)-ethylphenylglyoxylate ꢀ3f). The residue was puri-
®ed by column chromatography +petroleum ether/CHCl3
1:2), affording 3f as a white solid +95% yield). Mp107±
1088C; [Found: C, 66.5; H, 3.9. C29H19F5O4 requires C,
20
4.60]; [a]D 231.1 +c 1.1, CHCl3); IR +KBr): 2960, 2920,
2860, 1790 +CO), 1690 +CO), 1450, 1330, 1120, 1070, 760,
;
700 cm21 1H NMR +300 MHz, CDCl3) d 4.40 +d,
J12.6 Hz, 1H), 4.58 +d, J12.6 Hz, 1H), 4.70 +d,
J7.9 Hz, 1H), 6.30 +d, J7.9 Hz, 1H), 7.12±7.38 +m,
14H), 7.52 +d, J8.1 Hz, 2H), 7.60 +t, J7.5 Hz, 1H),
7.92 +d, J8.1 Hz, 2H); 13C NMR +75 MHz, CDCl3) d
70.0, 80.3, 84.1, 125.2, 126.6 +q, J211.2 Hz), 127.4,
127.6, 127.9, 128.2, 128.4, 128.4, 128.5, 128.6, 128.7,
128.8, 130.0, 132.3, 134.8, 135.4, 136.8 +q, J57.7 Hz),
141.9, 163.1, 186.3.
20
66.16; H, 3.64]; [a]D 243.0 +c 1.0, CHCl3); IR +KBr):
3060, 3040, 2960, 2920, 2880, 1740 +CO), 1690 +CO), 1505,
1200, 1180, 990, 940, 700 cm21 1H NMR +300 MHz,
;
CDCl3), 4.44 +d, J9.9 Hz, 1H), 4.57 +d, J9.9 Hz, 1H),
4.67 +d, J7.6 Hz, 1H), 6.16 +d, J7.6 Hz, 1H), 7.10±7.26
+m, 10H), 7.43 +t, J7.2 Hz, 2H), 7.64 +t, J7.2 Hz, 1H),
1
7.89 +d, J7.9 Hz, 2H); C NMR +75 MHz, CDCl3) 58.3,
80.6, 84.8, 111.0 +m), 127.5, 127.8, 128.2, 128.4, 128.5,
128.6, 128.7, 130.0, 132.4, 134.7, 135.4, 139.0 +m), 139.7
+m), 143.0 +m), 143.9 +m), 147.3 +m), 162.8, 185.9.
3.5.2.
ꢀ1R,2R)-1,2-Diphenyl-2-ꢀ4-methoxybenzyloxy)-
ethylphenylglyoxylate ꢀ3c). The residue was puri®ed by
column chromatography +petroleum ether/Et2O 1:1), obtain-
ing 3c as a white solid +65% yield). Mp88±908C; [Found:
C, 77.5; H, 6.5. C30H26O5 requires C, 77.24; H, 6.62];
3.5.6. ꢀ1R,2R)-1,2-Diphenyl-2-ꢀ3,4,5-trimethoxybenzyl-
oxy)-ethylphenylglyoxylate ꢀ3g). The crude residue was
puri®ed by column chromatography +petroleum ether/
AcOEt 3:1), affording 3g as a colorless viscous liquid
+79% yield). [Found: C, 73.3; H, 6.1. C32H30O7 requires
20
[a]D 256.0 +c 1.0, CHCl3); IR +KBr): 3060, 3020,
2940, 1740 +CO), 1690 +CO), 1510, 1250, 1200, 1180,
1
990, 700 cm21; H NMR +300 MHz, CDCl3) d 3.77 +s,
20
3H), 4.26 +d, J11.5 Hz, 1H), 4.47 +d, J11.5 Hz, 1H),
4.67 +d, J7.8 Hz, 1H), 6.28 +d, J7.8 Hz, 1H), 6.78 +d,
J12.7 Hz, 2H), 7.11±7.23 +m, 12H), 7.34 +t, J7.5 Hz,
2H), 7.58 +t, J7.5 Hz, 1H), 7.92 +d, J7.3 Hz, 2H); 13C
NMR +75 MHz, CDCl3) d 55.2, 70.3, 80.4, 83.2, 113.7,
127.2, 127.6, 127.8, 128.0, 128.1, 128.2, 128.3, 128.7,
129.1, 129.6, 129.8, 129.9, 130.1, 132.4, 134.7, 135.7,
136.9, 163.2, 186.5.
C, 72.99; H, 5.74]; [a]D 252.4 +c 1.2, CHCl3); IR
+KBr): 3060, 3010, 2940, 1740 +CO), 1690 +CO), 1595,
1
1455, 1330, 1240, 1200, 1130, 990, 760, 700 cm21; H
NMR +300 MHz, CDCl3) d 3.71 +s, 6H), 3.83 +s, 3H),
4.28 +d, J12.0 Hz, 1H), 4.52 +d, J12.0 Hz, 1H), 4.71
+d, J8.1 Hz, 1H), 6.31 +d, J8.1 Hz, 1H), 6.48 +s, 2H),
7.13±7.26 +m, 10H), 7.38 +t, J7.9 Hz, 2H), 7.61 +t
J7.9 Hz, 1H), 7.94 +d, J8.2 Hz, 2H); 13C NMR
+75 MHz, CDCl3) d 56.0, 60.7, 70.7, 80.4, 83.3, 104.5,
127.8, 128.0, 128.1, 128.3, 128.4, 128.5, 128.8, 130.1,
132.4, 133.4, 134.8, 135.7, 136.7, 153.2, 186.4.
3.5.3. ꢀ1R,2R)-1,2-Diphenyl-2-ꢀ4-isopropylbenzyloxy)-
ethylphenylglyoxylate ꢀ3d). The residue was puri®ed by
column chromatography +petroleum ether/CHCl3 1:1),
affording 3d as a colorless viscous liquid +98% yield).
[Found: C, 80.5; H, 6.2. C32H30O4 requires C, 80.31; H,
3.6. General procedure of reduction of phenylglyoxylates
3b±g
20
6.32]; [a]D 255.8 +c 1.0, CHCl3); IR +KBr): 3060,
3030, 2960, 1740 +CO), 1690 +CO), 1600, 1450, 1380,
1
1200, 1175, 990, 700 cm21; H NMR +300 MHz, CDCl3)
A solution of DIBAL +1.5 M in toluene, 0.23 mmol) was
slowly added by syringe to a solution of the phenyl-
glyoxylate 3 +0.23 mmol) in THF +5 mL) kept at 2788C
under N2 atmosphere. The reaction, monitored by TLC,
was quenched by addition of methanol +0.1 mL), diluted
with Et2O, extracted with NaOH 10%, brine and dried
over Na2SO4. After evaporation of solvent, the crude
mixture of a-hydroxyesters 4b±g was analyzed by 1H
NMR spectroscopy in order to measure the diastereo-
isomeric ratio.
d 1.24 +d, J6.9 Hz, 6H), 2.90 +sept, J6.9 Hz, 1H), 4.30
+d, J11.6 Hz, 1H), 4.50 +d, J11.6 Hz, 1H), 4.71 +d,
J7.9 Hz, 1H), 6.30 +d, J7.9 Hz, 1H), 7.12±7.23 +m,
14H), 7.31 +t, J8.2 Hz, 2H), 7.46 +t, J7.5 Hz, 1H), 7.93
+d, J8.2, 2H); 13C NMR +75 MHz, CDCl3) d 24.00, 33.9,
70.7, 80.4, 83.7, 126.4, 127.6, 127.7, 128.0, 128.3, 128.4,
128.7, 128.8, 130.2, 132.5, 134.6, 135.3, 135.7, 137.0, 140.2
164.1, 186.5.
3.5.4. ꢀ1R,2R)-1,2-Diphenyl-2-ꢀ4-phenylbenzyloxy)-ethyl-
phenylglyoxylate ꢀ3e). The crude residue was puri®ed by
column chromatography +petroleum ether/Et2O 8:1), reco-
vering 3e as a pale-yellow viscous liquid +74% yield).
[Found: C, 82.3; H, 5.4. C35H28O4 requires C, 82.01; H,
Acknowledgements
20
5.51]; [a]D 258.0 +c 1.0, CHCl3); IR +KBr): 3060,
Financial support from MURST +COFIN2000) and
Á
Universita della Basilicata +Potenza) is gratefully
acknowledged.
3040, 2920, 2880, 1740 +CO), 1690 +CO), 1600, 1490,
1450, 1200, 1180, 990, 760, 700 cm21
;
1H NMR