Based on the analysis of these spectra, compound 1 was suggested to be an hopan-type triterpenoid [25, 26].
The H2O2-induced spectra (compound F and some P species) are less stable.
Since the system based on imines 1– 4 required GC analysis for full quantification due to overlapping signals in the NMR spectra, compound 5 and benzylamine A3 were instead subjected to the TATI conditions.
The symbols CTP1, CTP2 and CTP3 correspond respectively to the cumulative number of true positives (TP) identified with E-value equal to or smaller than the specified cutoff when analyzing single-peptide spectra, compound spectra of two peptides, and compound spectra of three peptides.
In this way, 3- dimethylamino -1- 5-methyl-1- p-tolyl -1H-1,2,3-triazol-4-yl prop-2-en-1-one (6) was coupled with benzenediazonium chloride or p-toluidinediazonium chloride to give a product indistinguishable in all aspects (m.p., mixed m.p. and spectra) with compound (12a) and compound (12b), respectively.
Combining those spectra of isolated compounds and the published documents (Wu et al., 2013; Balakrishnan et al. 2014), compound 1 and 2 were identified as Monasfluol B and Monascus azaphilones C (Figs. 4a, b; 5, Additional file 1: Figure S1; Tables 2, 3).
The resulting solid so formed after 3 h and was collected, washed with water, and recrystallized to give product identical in all aspects (m.p., mixed m.p. and spectra) with the corresponding compound (10a) and compound (10b), which was obtained in method A. Brown crystals from ethanol, yield (75%); m.p. 215 217 °C.
Once the 73 spectra are selected for a given search method, one may then proceed to sample ten realizations of 24 ≈ 73/3 compound spectra, each made of either a single spectrum, two spectra, or three spectra as described earlier.
The number in parentheses is the number of compound spectra per realization of sampling when mixing only spectra of unique peptides (see text for more detail).
The infrared spectral analysis was obtained prior to neutralization of the compound and spectra confirmed the amide formation.
Unlike those reported characteristic emission of metal-doped luminescent nanomaterials [35, 36], these compound PL spectra with broad feature are assigned to different species defect states in ZnS nanocrystallites, which will be discussed in following section.
