Preparation of N-(2-benzoyl-1-methylvinyl)amino acid dicyclohexylammonium salts for peptide synthesis

The role of the imidazolyl nitrogen atoms of histidine-12 in ribonuclease S

“…Fragment (II) was prepared in essentially the same way as described for the synthesis of rat S-peptide (Voskuyl-Holtkamp et al, 1976,1977). The a-amino group of 16-(pyrid-3-yl)-L-alanine was protected with the Bmv group (Southard et al, 1971). N'and NT-Methyl-L-histidine were from Calbiochem A.G. (Lucerne, Switzerland) and checked for purity by t.l.c.…”

Synthetic approach to (-)-quassimarin based on intramolecular Diels-Alder strategy

“…A solution of the crude ester 13 (1.30 g) in dry THF (10 mL) was added dropwise to a suspension of LiAlH4 (0.255 g, 6.70 mmol) in dry THF (20 mL) at 0 °C, stirring was continued for 1 h, and then the reaction mixture was quenched with ether containing water. After filtration through Celite, the filtrate was concentrated in vacuo, followed by column chromatography (eluting with 2:3 AcOEt/n-hexane) to yield 0.05 g (4%) of 15 as a colorless oil: IR (CHCI3) [cm '1] 3400; NMR (100 MHz) 0.08 (6 H, s), 0.88 (9 H, s), 1.86 (3 H, d, J = 2.0 Hz), 3.24 (3 H, s), 3.46 (3 H, s), 5.12 (1 H, d, J = 10.0 Hz); mass specturm, m/z 189 [M+ -Si-(CH3)2C(CH3)3]; [a]23D +20.0°(c 1.70). Anal.…”

“…The organic phase was washed with brine and dried. Evaporation of the solvent followed by column chromatography (eluting with 2:3 AcOEt/n-hexane) yielded 6.80 g (100%) of the alcohol 17 as a colorless oil: IR (CHC13) [cm"1] 3400; NMR (60 MHz) 1.88 (3 H, br s), 2.65 (1 H, m, D20 exchangeable), 3.25 (3 H, s), 3.50 (3 H, s), 3.58 (2 H, m), 4.15 (1 H, dd, J = 9.0 and 6.0 Hz), 5.07 (1 H, d, J = 8.0 Hz), 5.17 (1 H, d, J = 17.0 Hz), 5.32 (1 H, d, J = 9.0 Hz), 6.36 (1 H, dd, J = 8.0 and 17.0 Hz); mass spectrum, m/z 186 (M+); [a]27D +12.6°(c 2.50); exact mass caled for C10H18O3 186.1255, found 186.1265.…”

“…Anal. Caled for C17H2406: C, 62.95; H, 7.46. Found: C, 62.46; , 7.18. (-)-(4/S)-8a-Acetoxy-l/9,5-dimethyl-20,3a-dimethoxy-lloxa-12-oxotricyclo[7.2.1.04,9]dodec-5-ene (5). The alcohol 23 (5.0 mg, 0.0177 mmol) was acetylated with acetic anhydride (0.005 mL, 0.0532 mmol), pyridine (0.005 mL, 0.0532 mmol), and a catalytic amount of DMAP as described for 24 to affored 6.0 mg (100%) of the acetate 5 as a colorless oil: IR (CHClg) [cm"1] 1770, 1735; NMR (400 MHz) 1.34 (3 H, s), 1.72 (3 H, br s), 1.81 (1 H, dd, J = 14.0 and 11.0 Hz), 2.00 (3 H, s), 2.47 (1 H, dt, J = 14.0 and 5.9 Hz), 2.79 (1 H, d, J = 1.0 Hz), 3.43 (3 H, s), 3.45 (3 H, s), 3.51 (1 H, d, J = 5.1 Hz), 3.56 (1 H, s), 4.12 (1 H, dd, J = 8.1 and 1.0 Hz), 4.59 (1 H, d, J = 8.1 Hz), 5.21 (1 H, dd, J = 11.0 and 5.9 Hz), 5.46 (1 H, m); mass spectrum, m/z 324 (M+); [a]28D -140.1°( c 0.70).…”

“…Caled for C7H1602: C, 63.59; H, 12.20. Found: C, 63.70; H, 12.15. erythro ] threo -2-Ethy 1-3-ethoxy bulan-1 -ol (lOe): 87% yield; bp 100 °C (18 Torr); NMR 4.2-3.0 (m, 5 ), 1.8 (s, 1 ), 1.6-0.6 (m, 12 H); 13C NMR (79.81, 78.86), (64.50, 64.24), (63.75, 63.72), (47.77, 45.26), (21.37,19.80), 17.60, (15.40, 14.56), (12. 26,11.63); MS, m/z 146 (M+, 0.1), 73 (100), 55 (14.4), 45 (87.8), 43 (16.0), 41 (14.5), 31 (16.0).…”