13. Researches on acetylenic compounds. Part I. The preparation of acetylenic ketones by oxidation of acetylenic carbinols and glycols

Ent-kauren-19-oic acid derivatives from the stem bark of Croton pseudopulchellus Pax

“…The optical rotation of -160 confirmed that compound 1 belonged to the ent series, previously synthesized from stevioside (Yun-Xing et al, 1995;Bowden et al, 1946).…”

“…Fractions 10 -19 (20% DCM: 80% Hex) gave ent-kaur-16-en-19-al (27.0 mg), 8R, 13R -epoxylabd-14-ene (11.6 mg) and (-)-7-epivaleran-4-one (13.2 mg (1) was oxidised using Jones reagent (Bowden et al, 1946) to yield compound 1a. A mixture containing ent-14S*,17-dihydroxykaur-15-en-19-oic acid (15 mg) was acetylated using pyridine (1 ml) and acetic anhydride (1 ml) and the reaction left to stand for 24 hours.…”

An efficient stereoselective total synthesis of 11β-methoxycurvularin

“…To a suspension of Mg metal (2.5 g, 15.62 mmol) in dry THF (50 mL) was added ethyl bromide (1.7 mL, 23.43 mmol) at 0 o C. The mixture was stirred for 30 min at room temperature and then compound 13 in dry THF was added at 0 o C. After stirring for 2 h at room temperature, paraformaldehyde was added slowly at 0 o C. The resulting mixture was stirred for another 5-6 h. After completion, the reaction was quenched with saturated NH 4 Cl (20 mL) and extracted with EtOAc (2 × 50 mL) and dried over Na 2 SO 4 . The solvent was evaporated under reduced pressure and the residue was purified by column chromatography (EtOAc/hexanes, 2:8) as eluent to afford compound 14 as a colourless oily liquid (1.65 g (72% (15). To a suspension of LiAlH 4 (540 mg, 14.21 mmol) in THF (30 mL) was added a solution of 14 (1.8 g, 9.47 mmol) in THF (10 mL) in a dropwise manner.…”

“…Subsequent deprotection of the benzyl group and reduction of the triple bond were achieved by hydrogenation using 10% Pd/C 14 in ethyl acetate to afford the alcohol 19 in 70% yield. Oxidation of 19 using Jones reagent 15,16 (CrO 3 , H 2 O, H 2 SO 4 ; acetone, 0 o -rt) gave the desired carboxylic acid 6 in 80% yield.…”

Kinetic Study on Michael-type Reactions of 1-Phenyl-2-propyn-1-one with Alicyclic Secondary Amines: Effect of Medium on Reactivity and Mechanism

“…1-Phenyl-2-propyn-1-one (2) was readily prepared from oxidation of 1-phenyl-2-propyn-1-ol, 22 which was obtained from the reaction of benzaldehyde with ethylmagnesium bromide in dried diethyl ether as reported in the literature. 23 The purity of 2 was checked by means of the melting point and 1 H NMR spectra.…”