Stereoselective Synthesis of Podoblastins and Their Antiblast Activity

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

“…Consequently, the present total synthesis was performed in only five steps and in an overall 40% yield with 98% ee. Compared with the reported total synthesis [ 17 ], the overall yield and efficiency were improved remarkably.…”

“…The first and sole chiral synthesis of ( R )-podoblastin-S ( 2d ) was performed by Ichimoto’s group, starting from ( S )-1,3-dioxolane-4-methanol, a highly expensive chiral synthon, through 14 steps with an overall yield of 5% [ 17 ]. Our synthesis of 2d involved a catalytic asymmetric Mukaiyama aldol addition as a crucial step, and was completed in a total of five steps.…”

“…Pale yellow crystals; mp 90–93 °C (lit. [ 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.…”

“…Pale yellow crystals; mp 38–39 °C [lit. [ 17 ], 40.5–41.5 °C]; −28.5 ( c 1.0, CHCl 3 ) [lit. [ 14 ], −30.09 ( c 1.19, CHCl 3 )]; 1 H-NMR (500 MHz, CDCl 3 ): δ = 0.87 (t, J = 6.7 Hz, 3H), 0.97 (t, J = 6.7 Hz, 3H), 1.19-1.83 (m, 18H), 2.55–2.70 (m, 2H), 2.96–3.09 (m, 2H), 4.34–4.50(m, 1H), 16.2 (s, 1H); 13 C-NMR (125 MHz, CDCl 3 ): δ = 13.7, 14.1, 17.9, 22.6, 25.0, 29.2, 29.30, 29.34, 29.4, 31.8, 36.7, 37.9, 38.5, 73.6, 103.1, 164.3, 195.2, 204.6; IR (neat): ν max = 2924, 2855, 1713, 1557, 1464, 1273, 1238, 1063, 912 cm −1 ; HRMS (ESI): m / z calcd for C 18 H 30 O 4 [M + H] + 311.2222; found: 311.2209; 98% ee; HPLC analysis (Daicel, AD-H, flow rate 1.0 mL/min, solvent: hexane/EtOH = 20/1) t R (racemic) = 14.02 min and 16.52 min.…”

Characterization of Secondary Metabolites Produced by Foliar Endophytes of Red and Black Spruce

“…The absolute configuration of compound 6 at C-6 was determined to be R based on comparison of its experimentally determined optical rotation, [] 25 D -30 (c 0.04, CHCl3), to structurally similar compounds with a single chiral center. The absolute stereochemistry of podoblastin A at C-6 was determined to be R by stereoselective synthesis which had an optical rotation of []D -27.08 (c 1.12, CHCl3; Ichimoto et al, 1988;Miyakado et al, 1982). Dictyopyrone A shares the same core structure and is of the S configuration at C-6.…”