An efficient asymmetric aldol reaction of Chan's diene promoted by chiral Ti(IV)–BINOL complex

Asymmetric Total Syntheses of Two 3-Acyl-5,6- dihydro-2H-pyrones: (R)-Podoblastin-S and (R)- Lachnelluloic Acid with Verification of the Absolute Configuration of (−)-Lachnelluloic Acid

“…503) using a glass filter, being washed with hexane (10 mL × 3). The filtrate was concentrated under reduced pressure to give the crude product 4 (5.03 g, 92%) [ 13 , 14 ], which was used for the next reaction without any purification.…”

“…[ 17 ] mp 88–89 °C; −82.8 ( c 1.0, CHCl 3 )) (lit. [ 14 ] −83.02 ( c 1.69, CHCl 3 )); 1 H-NMR (400 MHz, CDCl 3 ): δ = 0.99 (t, J = 7.3 Hz, 3H), 1.42–1.72 (m, 3H), 1.79–1.88 (m, 1H), 2.47 (dd, J = 11.0 Hz, 18.3 Hz, 1H), 2.71 (dd, J = 2.8 Hz, 18.3 Hz, 1H), 3.43 (d, J = 18.8 Hz, 1H), 3.58 (d, J = 18.8 Hz, 1H), 4.62–4.68 (m, 1H); 13 C-NMR (100 MHz, CDCl 3 ): δ = 13.6, 18.0, 36.5, 43.5, 47.0, 75.3, 167.3, 200; IR (neat): ν max = 2955, 2668, 1682, 1582, 1389, 1287, 1254, 1223, 1128, 1042, 878, 829 cm −1 ; HRMS (ESI): m / z calcd for C 8 H 12 O 3 [M + Na] + 179.0684; found: 179.0682. 1 H-NMR and 13 C-NMR spectra: see supporting information .…”

“…This background led us to investigate the asymmetric total syntheses of a couple of chiral 3-acyl-5,6-dihydro-2 H -pyrones, i.e., unnatural ( R )-podoblastin-S ( 2d ) [ 10 ] and natural ( R )-lachnelluloic acid ( 3 ) [ 12 ], using a Ti-mediated reaction. The present two syntheses utilize efficient Ti(O i Pr) 4 /( S )-BINOL‒catalyzed asymmetric Mukaiyama aldol addition as a crucial step, developed by Soriente and Scettri’s group [ 13 , 14 , 15 , 16 ].…”

Practical and robust method for stereoselective preparations of ketene silyl (thio)acetal derivatives and NaOH-catalyzed crossed-Claisen condensation between ketene silyl acetals and methyl esters

“…The impressive progress in this area was reviewed: 7 precursors for Mukaiyama aldol reaction, 8 cyclopentannulation, 9 benzannulation, 10 oxabicyclo[3.2.1]octan-3-one formation, 11 tetrahydrofuran formation, 12 furanone formation, 13 Michael addition, 14 [4þ2]-or [3þ3]-cycloaddition, 15 Claisen-type reactions, 16 etc. 17 As depicted in Scheme 4, Soriente's group disclosed a notable Ti(O i Pr) 4 -BINOL-catalyzed asymmetric aldol addition of 3a to aldedydes, 18 The most general method for preparing 3 involves a two-step sequence: TMSCl-Et 3 N and TMSCl-LDA at À78 C. 10,20 Although our previous method (Scheme 2) involved the use of tert-butyl b-ketoesters, we reinvestigated the possibility of using other, more accessible alkyl (Me and i Pr) b-ketoesters 2. This objective is based on the conventional Weiler's protocol for dianion generation using 2, 21 which can be performed at a practical temperature (0-5 C); initial monoanion formation of the active methylene position suppresses the side self-Claisen condensation between b-ketoesters 2 due to intermolecular anion-anion repulsion.…”

Asymmetric syntheses of the lactone core of tetrahydrolipstatin and tetrahydroesterastin and of the oriental hornet Vespa Orientalis pheromone

“…It should be noted that silylated δ-hydroxy-β-keto esters are valuable intermediate products which were used in the synthesis of many biologically active compounds, such as vitamin D analog [93], anachelin [94,95], (-)-cochleamycin A [96], goniothalamin [97], parasorbic acid and colletodiol [98], and lactone analogs of compactin and mevinolin [99][100][101][102][103][104][105].…”