**5. Conclusions**

Two new thiopeptide antibiotics were isolated from a new actinomycetes bacterium, which was isolated from a sand sample collected at a Wadden Sea beach. While their planar structures were elucidated by NMR and MS data, their absolute configuration was determined by degradation by ozonolysis and hydrolosis followed by Marfey's method. Their spectrum of biological activities is rare, because they are cytotoxic but possess virtually no antibacterial activities.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/1660-3397/18/6/280/s1, Figure S1: Fractionation analysis of *Streptomonospora* sp. M2 crude extract. Table S1: Antimicrobial activity of **1** and **2**, Figure S2: Observed TOCSY, HMBC and ROESY correlations for **1**, Figure S3: Known compounds structurally related to litoralimycins, Figure S4: HPLC–MS and UV–Vis chromatograms of *Streptomonospora* sp. M2 and HRESIMS data, Figure S5: HPLC–ESIMS spectrum of litoralimycin A (**1**), Figure S6: 1H NMR spectrum (700 MHz, DMSO-*d*6) of litoralimycin A (**1**), Figure S7: 13C NMR spectrum (175 MHz, DMSO-*d*6) of litoralimycin A (**1**), Figure S8: COSY NMR spectrum (700 MHz, DMSO-*d*6) of litoralimycin A (**1**), Figure S9: ROESY NMR spectrum (700 MHz, DMSO-*d*6) of litoralimycin A (**1**), Figure S10: HSQC NMR spectrum (700 MHz, DMSO-*d*6) of litoralimycin A (**1**), Figure S11: HMBC NMR spectrum (700 MHz, DMSO-*d*6) of litoralimycin A (**1**), Figure S12: Marfey derivatization for determination of type and configuration of amino acids in litoralimycin A (**1**), Figure S13: HPLC-ESIMS spectrum of litoralimycin B (**2**), Figure S14: 1H NMR spectrum (700 MHz, DMSO-*d*6) of litoralimycin B (**2**), Figure S15: 13C NMR spectrum (175 MHz, DMSO-*d*6) of litoralimycin B (**2**), Figure S16: COSY NMR spectrum (700 MHz, DMSO-*d*6) of litoralimycin B (**2**), Figure S17: ROESY NMR spectrum (700 MHz, DMSO-*d*6) of litoralimycin B (**2**), Figure S18: HSQC NMR spectrum (700 MHz, DMSO-*d*6) of litoralimycin B (**2**), Figure S19: HMBC NMR spectrum (700 MHz, DMSO-*d*6) of litoralimycin B (**2**), Figure S20: MS/MS data for **1** and **2** with fragmentation of [M + Na]+ ions.

**Author Contributions:** Conceptualization, J.W. and F.S.; execution of experiments, S.K.; structure elucidation, F.S.; resources, M.S.; writing—original draft preparation, S.K.; writing—review and editing, M.S., J.W., F.S.; supervision, J.W., F.S.; funding acquisition, M.S., J.W. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by a personal stipend to S.K.

**Acknowledgments:** We would also like to thank Klaus-Peter Conrad for the measurement of HRESIMS data, Wera Collisi for conducting the bioassays, and Christel Kakoschke for the measurement of NMR spectra. We gratefully acknowledge the assistance of Romy Schade in cultivation of the strain and Silke Reinecke for helping to isolate the metabolites.

**Conflicts of Interest:** The authors declare no conflict of interest.
