p-Toluenesulfonic acid → HCID 101025554, compound

Participants

Reaction Steps

Monic acid A (3.44 g) was dissolved in 2,2-dimethoxypropane (30 ml) and ethyl acetate (30 ml) with a few crystals of p-toluene sulphonic acid. After one hour the solution was diluted with ethyl acetate and washed with brine then dried (MgSO4). The solvent was removed in vacuo and the acetonide dissolved in water-methanol (1:1, 40 ml) then treated with potassium bicarbonate (1.0 g, 1 eq). The solution was evaporated to dryness and potassium selenocyanate (4.32 g, 3 eq), tert-amyl alcohol-water (9:1, 150 ml) added and reaction refluxed for 42 hours. After filtering, the reaction mixture was diluted with ethyl acetate and extracted with water (4×25 ml). The combined aqueous phases were acidified (pH2, 5 M-HCl) and extracted with ethyl acetate (4×25 ml) and the combined extracts dried (MgSO4). The solvent was removed in vacuo to give 6,7-O-ispropylidene monic acid C, νmax (CHCl3) 1695, 1640, 1380, 1370, 1220 and 1055 cm-1 ; δ H (CDCl3) 0.98 (3H, d, CH3 -17), 1.13 (3H, d, CH3 -14), 1.33 and 1.48 (6H, d, acetonide CH3 's), 2.17 (3H, s, CH3 -15), 5.45 (2H, m, H-10, H-11), 5.75 (1H, s, H-2), 4.35 (2H, broad, CO2H, OH); δC (CDCl3) 170.5 (C1), 158.3 (C3), 134.9, 128.8 (C10, C11), 117.5 (C2), ##STR7## 76.5 (C5), 75.7 (C7), 74.1 (C6), 71.1 (C13), 66.5 (C16), 44.3 (C12), 36.8 (C8), 34.1 (C9), 28.3, 26.3 (C(CH3)2), 20.1 (C14), 19.3 (C15), 16.3 (C17); m/e (relative intensity) 353 (9) (Found: 353.1995. M+ --CH3 requires 353.2026) 350 (4) (M+ --H2O). The acetonide was dissolved in 80% acetic acid (100 ml) then left overnight. The solution was evaporated to dryness and chromatographed on silica (50 g) eluting with 0-10% methanol-chloroform. The fractions containing pure product (tlc) were combined and evaporated to give monic acid C m.p. 101°-102° C. (2.57 g, 72%) (Found: C, 61.8; H, 8.4. C17H28O6 requires C, 62.2; H, 8.6%).

Provenance & Evidence