We have constructed a library of isolated natural products obtained from microbial sources in order to perform efficient screenings. During the investigation of rare microbial products with promising biological and pharmacological properties, we have developed an advanced system for compound identification based on accumulated HPLC-MS profiling data and strain information designated as 'MBJ's special selection'. Using this screening method, we have already succeeded in discovering novel eremophilane derivatives MBJ-0009 and MBJ-0010 from Nectria sp. f26111, MBJ-0011, MBJ-0012 and MBJ-0013 from Apiognomonia sp. f24023, cytotoxic chaetoglobosin derivatives MBJ-0038, MBJ-0039 and MBJ-0040 from Chaetomium sp. f24230, and a cytotoxic hydroxamate MBJ-0003 from Micromonospora sp. 29867. During our continuous search for new substances, two metabolites named MBJ-0173 (1) and MBJ-0174 (2) were isolated together with plactin B, from the culture broth of Mortierella alpina f28740 (Figure 1a). In this paper, the fermentation, isolation, structure elucidation and preliminarily biological activities of 1 and 2 are described.