Defense Secretion in Three Species of Polydesmids (Diplopoda, Polydesmida, Polydesmidae)

Supplemental Data

Notes on Identifications Compounds 1-8 have perfect MS match factors (more than 900 out of 1000 in NIST, or more than 90 out of 100 in AMDIS software). This means that there are no extra or missing peaks in any8 EI MS spectra. Furthermore, compounds 1, 2, 5, and 7 had excellent RI matches (see literature data in Supplemental Data Table 1), and all data were collected on the same type of column and at the same column length. Differences in retention times must be at least ± 20 RI units (a well-known GC criterion). There was no GC RI data collected for compound 4 under the same chromatographic conditions. Measured RI for compound 4 (1138) was in the middle of the RI range reported in the literature (Supplemental Data Table 1)(1116 and 1170), both from different types of column, as well as from the same column type but withdifferent column length. Compound 6 had a perfect RI match factor, but data reported in the literature were from an old packed column with similar polarity. Furthermore, compounds 4 and 6 are homologous with difference in a CH2 group. In RI GC language, this means about one hundred RI unit differences (similar differences between two hydrocarbons).

There are no RI literature data for compounds 3 and 8. Thus, we compared spectral data for these compounds to the closely related chemical 7. All compounds (1-7) are aromatic and have intensive molecular ions. Therefore, we inferred the molecular weight of each compound, and did not need to acquire chemical ionization MS data. Compound 3 hasa molecular weight of 131, which indicatesan odd number of nitrogen atoms. The MS spectrum (and fragmentation pathway, Supplemental Data Fig. 1) of compound 3 strongly support the proposed structure, and eliminate all other isomeric structures (o, m, p, or any other).

Compound 7 hasa molecular weight of 133 (odd number of nitrogen atoms) and compared with Compound 3, Compound 7has two extra H atoms, which indicates that the former chemical has anhydroxyl instead of a keto functional group. In addition, the presence of the hydroxyl is indicated by the M-1, M-17 and M-18 ions, and all are stabilized by resonance (Supplemental Data Fig. 2). Ions 105, 77, and 51 have the same structure as shown for Compound 3. In addition, MS spectrum of 7 also supports the proposed structure, and eliminates all other isomeric structures (o, m, p, or any other).

Compound 8 hasa molecular weight of 237 (odd number of nitrogen atoms). Ions 105 (base peak) and 116 (~40%) are derived from the molecular ion (~25%) by simple fragmentation of both ester bonds, with a neutral lost 132 and 121, respectively. The third ion according to intensity is 77 (~30%) and is actually the last one with important intensity, belonging to [C6H5]+. Again,the MS spectrum of 8 strongly supportsthe proposed structure, and eliminates all other isomeric structures.

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