Synthesis and Structure of Flavan-4-ols and 4-Methoxyflavans as New Potential Anticancer Drugs

NMR investigation and theoretical calculations of the effect of solvent on the conformational analysis of 4',7-di-hydroxy-8-prenylflavan

“…From these results, the enthalpy of the solute-solvent interaction (∆H i ) could be estimated to be equal to -2.5, -1.4, and -1.0 kcal/mol, respectively. These results show that the A ring and solvent interactions are thermodynamically more favored in 1a-acetone than in 1b-DMSO, wich, in turn, is more favored than in 1c-CHCl 3 .…”

“…Differently from that reported for spectra obtained in CDCl 3 and DMSO-d6 [10][11][12] , the magnetic non-equivalence of the two geminal hydrogens H-1" was made explicit in acetone-d6. The signals at δ H 3.34 (H-1"a) and 3.29 (H-1"b), making up the AB portion of an ABX system with geminal coupling 2 J H,H = 13.53 Hz and the coupling of these two hydrogens with H-2", 3 J H,H = 7.43 Hz, were observed. NOESY data of 1 in acetone-d6 presented in Table 1 show that H-1"a is closer to HO(C-7), while H-1"b is closer to H-2'/6'.…”

“…The methodology used in the isolation and determination of the physical and chemical data of 1, including NMR data for CDCl 3 and DMSO-d6, was described elsewhere 10 13 C NMR (100 MHz) δ: 157.82 (C-4'), 154.77 (C-7), 154.54 (C-9), 134.39 (C-1'), 130.62 (C-3"), 128.16 (C-2'/6'), 127.54 (C-5), 124.51 (C-2"), 116.28 (C-8), 115.97 (C-3'/5'), 113.86 (C-10), 108.41 (C-6), 78.29 (C-2), 31.02 (C-3), 26.02 (C-4"), 25.53 (C-4), 23.10 (C-1") and 18.05 (C-5").…”

“…They are very important from the biological viewpoint, presenting anti-oxidant, antibacterial, antitumoral and anti-HIV activities [1][2][3] . These substances are found in complex mixtures mainly because of the fact they condense with proteins and sugars.…”

“…The phytochemical study of the extract gave 4',7-dihydroxy-8-prenylflavan 1 (Figure 1) [10][11][12] . The NMR study of this flavan presented varying results depending on whether the spectra were obtained in CDCl 3 or DMSO-d6. The current paper describes an attempt to verify whether this behavior is a result of conformational variations.…”