1 2/6 3/5 4 OHC 60.1, CH2 118.1, CH 34.5, CH3 133.eight, C 129.two, CH 128.3, CH 128.1, CHH (J in Hz) 3.40, m six.97, s two.73, s 7.42, d (7.five) 7.30, t (7.five) 7.34, t (7.5) 4.48, br sMeasured at 500 MHz for 1H and 125 MHz for 13C.To decide the absolute configuration of 1, the electronic circular dichroism (ECD) was experimentally recorded and it showed adverse Cotton effects at 203 and 288 nm (Figure 3). The theoretical ECD was then calculated using the time-dependent DFT (density function theory) system at the B3LYP/6-31G(d) level and was compared with that from the experimental data. The side chain at C-3 in 1 was truncated to a methyl (1a and 1b) (Figure four) since it contributes small towards the ECD spectrum [15,16]. The results showed that, even though a slightly peaked shift was observed, the calculated curve of 1a (with 3R-configuration) was in great agreement with that with the experimental a single (Figure 3), which indicated that the absolute configuration at C-3 of 1 was R.Formula of 2-(3-Methyl-3H-diazirin-3-yl)ethan-1-ol Figure three. Experimental and calculated electronic circular dichroism (ECD) spectra of 1a (3R) and 1b (3S).six 3 0 exptl calcd 3R calcd 3S/M-1cm-195 -3 -6 –Wavelength/nmMar. Drugs 2013, 11 Figure 4. Model compounds 1a and 1b for ECD calculations.O NH N O 1a (3R)RO NH N O 1b (3S)SCompound two was obtained as white amorphous powder and its molecular formula C10H10O5 was determined around the basis with the good HRESIMS. Detailed analysis of the NMR spectroscopic information (Table two) revealed that the structure of two was similar to (S)-3-ethyl-7-hydroxy-6-methoxyphthalide (11, Figure 1) [17]. On the other hand, the C-6 OMe group in 11 was replaced by OH group in two as evidenced by the truth that the resonances corresponding towards the C-6 OMe group at H 3.84/C 56.two inside the NMR spectra of 11 disappeared in that of two. In addition, the proton signals at H five.51 (H-3), 1.83/2.30 (H-8), and 0.95 (H-9) at the same time as the carbon signals at C 83.three (CH, C-3), 25.9 (CH2, C-8), and 9.1 (CH3, C-9) in the NMR spectra of 11 had been missing in that of two. Rather, signals resonating at C 108.6 (C) to get a ketal carbon (C-3), at H 1.74/C 25.six for a methyl group (CH3-8), and at H 2.94/C 52.4 for an OMe group (OCH3-9), have been observed within the NMR spectra of 2 (Table 2). The HMBC correlations from H-8 and H-9 to C-3 and from H-8 to C-3a supported the above deduction (Figure 2). The structure of 2 was as a result determined as 6,7-dihydroxy-3-methoxy-3-methylphthalide. To unambiguously establish the absolute configuration, compound two was also submitted to ECD measurement and calculation.Formula of 236406-56-7 Nonetheless, no obvious Cotton impact was observed in the experiment.PMID:23558135 Hence, ECD was not applicable to resolve the absolute configuration of compound 2. By comparison of its optical rotation ([]D27 -8.three, c 0.12, CHCl3) with that from the (S)-3-ethyl-7-hydroxy-6-methoxyphthalide (11) ([]D25 -71.5, c 0.10, CHCl3) [17], the S-configuration at C-3 was tentatively deduced to this compound. Table 2. 1H- and 13C-NMR data of compound two in DMSO-d6 a.No. 1 three 3a four five C 167.six, C 108.6, C 132.9, C 121.2, CH 125.7, CHaH (J in Hz)six.84, d (eight.five) 7.01, d (8.five)No. six 7 7a 8C 146.six, C 151.1, C 114.6, C 25.six, CH3 52.four, CHH (J in Hz)1.74, s 2.94, sMeasured at 500 MHz for 1H and 125 MHz for 13Cpounds three and four had been previously reported as synthetic solutions and had been obtained and described here for the initial time as naturally occurring fungal metabolites [12?4]. The NMR information for compound 3 was not published previously and also the completely assigned 1H and 13C NMR information for this compound were offered in the Experim.