840
HETEROCYCLES, Vol. 65, No. 4, 2005
3-methyl-2-t-butyldimethylsilyloxyfuran (20 mg, 0.09 mmol) and N-benzylideneaniline (34 mg, 0.18
mmol) to give 20 (26 mg, 99%) as a 21/79 erythro/threo mixture and as a glassy solid after purification
by preparative layer chromatography (AcOEt/heptane 35/65); Rf erythro/threo mixture: 0.60
1
(AcOEt/heptane 50/50). H-NMR (300 MHz, CD3OD) δ erythro, [threo]: 7.50-7.30 (m, 6H, H-Ph, H-4,
[H-Ph] and [H-4]); 7.10-6.45 (m, 5H, H-Ar and [H-Ar]); [5.35 (ddd, J=3.8, 1.8, 1.8 Hz, 0.79H, H-5)];
5.25 (ddd, J=7.0, 1.8, 1.8 Hz, 0.21H, H-5); [4.75 (d, J=3.8 Hz, 0.79H, H-6)]; 4.35 (d, J=7.0 Hz, 0.21H,
H-6); 1.95 (dd, J=1.6, 1.6 Hz, 0.63H, CH3); [1.90 (dd, J=1.6, 1.6 Hz, 2.37H, CH3)].
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