“…A mixture of a portion of this sample of 30 (58.5 mg, 0.188 mmol), paraformaldehyde (11.3 mg, 0.376 mmol), and absolute EtOH (0.6 mL) was sealed in a 5-mL ampule and heated at 80 °C for 2-4 h. After cooling to 23 °C unreacted paraformaldehyde was removed by filtration, and the filtrate was concentrated to give the crude oxazolidine 31: NMR (250 MHz, CDC13) 5.78 (d, 7=10 Hz, C=CH), 4.43 (AB q, 7 = 6. 25 Hz, = 14.9 Hz, NCHHO), 3.3-3.4 (m, NCH), NCTTH),NCH.H),2.34 (d,7= 13.6 Hz, Cf/HC=C), 2.09 (d, 7 = 13.6 Hz, CHHC=C), 2.2-2A (m), 1.7-2.0 (m), 1.2-1.4 (m), 1.10 (s, Me), 0.94 (d, 7 = 6.2 Hz, CH Me), 0.88 (t, 7 = 6.5 Hz, CH 2Me), 0.15 (s, Me3Si); MS (isobutane Cl), m/z 324 (MH), 126, 125, 114, 84, 83, 73, 70. A solution of this oxazolidine sample, camphorsulfonic acid (21.8 mg, 0.087 mmol), and absolute EtOH (0.6 mL) was sealed in a glass ampule and heated at 80 °C for 1 day. The reaction was then concentrated, the residue was partitioned between CH2C12 (20 mL) and NaHC03 (5 mL, saturated aqueous), and the organic layer was dried (Na2S04).…”