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1.25 (m, 6H), 0.88 (t, J = 6.9 Hz, 3H); 13 C NMR (75 MHz, DMSO-d6, 325 K): δ 171.7, 153.2,
136.0, 135.9, 134.2, 130.2, 129.8, 127.2, 126.1, 125.3, 123.9, 120.0, 79.9, 67.7, 51.6, 31.9, 30.4,
27.9, 27.7, 21.5, 15.6, 13.4, 12.4; IR (thin film): ν 2926, 1744, 1696, 1240 cm -1 ; MS m/z (%) 458
(6), 394 (42), 376 (30), 276 (78), 91 (50), 57 (100); EI-HRMS calcd for C22H34NO4 m/z [M-91] +
376.2488; found 376.2479.
Compounds 120-125 were prepared as part of a preliminary study which was later discontinued;
These compounds were characterized only by their 1 H NMR spectrum:
The TBS protected diol 118 was prepared according to a previously reported procedure
(Lafontaine, J. A.; Provencal, D. P.; Gardelli, C.; Leahy, J. W. J. Org. Chem. 2003, 68, 4215).
Alcohols 116a and 116b were prepared according to a previously reported procedure
(Aurrecoechea, J. M.; Perez, E.; Solay, M. J. Org. Chem. 2001, 66, 564).
Bn
N
Ph
55a
4-Benzyl-2-phenyloxazol-5(4H)-one (55a). N-Bz-phenylalanine 119 (489 mg, 1.82 mmol) was
dissolved in CH2Cl2 (10 mL) at rt and DCC (374 mg, 1.82 mmol) was added followed by DMAP
(11 mg, 0.09 mmol). Dicyclohexylurea byproduct formed immediately as a white precipitate.
After 10 min, the reaction mixture was filtered over a short pad of silica gel using a fritted funnel
and eluted with hexanes-EtOAc (3 : 1). The filtrate was concentrated under vacuum to afford 55a
(365 mg, 80%) as a white solid. This compound was used in the next step without additional
purification.
O
O
193