Synthesis of two useful, enantiomerically pure derivatives of (S)-4-hydroxy-2-cyclohexenone

Synthetic Strategies toward Natural Products Containing Contiguous Stereogenic Quaternary Carbon Atoms

“…Enantiomerically pure chiron 21 , prepared from quinic acid, [26] was utilized to generate an octahydroazulenone core 23 via a free-radical cyclization of cyclopropyl intermediate 22 . Alkylation of the dimethylhydrazone derivative of 23 with bromide 20 gave ketone 24 , which upon base-promoted cyclization, afforded tricyclic intermediate 25 .…”

Efforts toward rapid construction of the cortistatin A carbocyclic core via enyne-ene metathesis

“…9 (1.01 g, 5.29 mmol, 1.0 equiv) in toluene (21 mL) was added 4-methoxybenzyl 2,2,2-trichloroacetimidate [4] (2.24 g, 7.93 mmol, 1.5 equiv) and La(OTf) 3 (164 mg, 0.28 mmol, 0.053 equiv). The mixture was stirred at 50 °C for 12 h. The reaction mixture was concentrated, and the crude residue was purified by flash chromatography (hexanes 99:1 98:2 hexanes/EtOAc) to give 10 as a colorless oil (1.60 g, 98% yield).…”

Synthetic Studies of Natural 10-Membered Lactones, Mueggelone, Microcarpalide, and Sch 642305, Which Have Interesting Bioactivities

“…Cyclohexenone 73 is known to be preparable from a natural product, quinic acid. 92,93) Silyl ketene acetal 74, which was easily prepared from commercially available (S)-4-penten-2-ol, was subjected to Mukaiyama-Michael addition 94) to enone 73 with concomitant silyl transfer to afford an inseparable 3.7:1 mixture of silyl enol ether 75 and its anti-isomer. Stereoselective allylation of 75 was successful by employing TASF 95,96) to give cyclohexanone 76 diastereoselectively.…”