Total synthesis of (+)-pericosine B and (+)-pericosine C and their enantiomers by using the Baylis–Hillman reaction and ring-closing metathesis as key steps

Palladium‐Catalyzed Allylic Substitution for the Synthesis of Pericosines

“…The multiplicities are abbreviated as follows: s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet, dd = doublet of doublets, td = triplet of doublets. Assignment of the 1 H and 13 Cr esonances for complex structures were confirmed by extensive 2D experiments (COSY,H MQC, and HMBC). IR spectra were obtained by using aF TIR spectrophotometer with at hin film or by using KBr pellets and recorded in cm À1 .O ptical rotations were measured with ad igital polarimeter with sodium light (589.3 nm) at 20 8C.…”

“…The crude product was purified by column chromatography (SiO 2 ,e thyl acetate/hexanes, 1:2; R f = 0.5) to afford 16 (6.6 mg, 0.014 mmol, 38 %) as ac olorless viscous liquid. a ½ 20 D = À88.08 (c = 0.3, CHCl 3 ); 1 HNMR (CDCl 3 ,3 00 MHz): d = 1.27 (s, 3H), 1.28 (s, 3H), 1.32 (s, 3H), 1.41 (s, 3H), 3.15 (d, J = 9.2 Hz, 1H), 3.50 (dd, J = 1.9, 9.2 Hz, 1H), 3.65 (s, 3H), 3.82 (s, 3H), 4.56 (d, J = 4.9 Hz, 1H), 4.72 (d, J = 6.5 Hz, 1H), 4.80 (dd, J = 4.9, 1.9 Hz, 1H), 5.00 (ddd, J = 6.5, 4.9, 1.5 Hz, 1H), 5.77 (dd, J = 2.2, 4.9 Hz, 1H), 6.74 (s, 1H), 7.08 (d, J = 2.2 Hz, 1H), 7.45 (t, J = 7.8 Hz, 2H), 7.55-7.60 (m, 1H), 8.09 ppm (d, J = 1.4 Hz, 2H); 13…”

“…[10] The required 1,7-dienes for RCM have been prepared by the Nozaki-Hiyama-Kishi (NHK) reaction [11,12] or Morita-Baylis-Hillman (MBH) reactions. [13] Recently,o ur group reported the utilization of the vinylalumination of an optically active aldehyde to generate the 1,7-dienes and the subsequent RCM to construct the cyclitol skeletons. [14a] Here, we present our progress with this approachi nt he preparation of (+ +)-pericosine A, and the combination of vinylalumination and palladium-catalyzed allylic substitution to prepare( À)-pericosine C from inexpensive d-ribose.…”

“…One interesting product 15 was isolated in 38 %yield when Pd(PPh 3 ) 2 Cl 2 was the catalyst (Scheme7). The structure of 15 was established on the basis of NMR spec-troscopy.I nt he 13 CNMR spectra, compound 15 showed two ester carbons around d = 165 ppm and an ew absorption at d = 195.8 ppm, which suggested ak etone moiety and that 15 could be ad imer of 14.T he DEPT spectra indicated that there are nine methine carbons and six methyl carbonsa nd no methylene carbon within 15.I nt he 1 HNMR spectra, the presence of the six methyl absorptions resulting from the two methyl esters and the two acteonides reconfirmed its dimeric structure. The absorptions at d = 6.68 and 6.98 ppm were attributed to the two olefinich ydrogens.…”

Synthesis of Marine-Derived Carbasugar Pericosines

“…In 2012, Vankar et al reported a unique approach to synthesizing both enantiomers of (þ)-2 and (þ)-3 from D-ribose via the Baylis-Hillman reaction and RCM [121]. This is a variation on their previous work involving the enantiodivergent synthesis of shikimic acid and 5-epi-shikimic acid mentioned above [110].…”