Deoxypseudophrynaminol, 1, is a potent antibacterial agent that inhibits the in vitro growth of vancomycin-resistant Enterococci and methicillin-resistant Staphylococcus aureus with MIC values ~ pg/mL.Nosocomial infections caused by vancomycin-resistant Enterococci and methicillin-resistant Staphylococcus aureus are serious health problems for the hospitalized and immunocompromised patient J, 2Thus, the discovery of clinically useful agents against these multidrug-resistant pathogens is of paramount importance.In this study, we have discovered that deoxypseudophrynaminol, 1,3 inhibits the in vitro growth of patientisolated vancomycin-resistant Enterococcusfaecium (VRE1), vancomycin-resistant Enterococcusfaecalis ATCC 51299 (VRE2), and two patient isolates of methicillin-resistant Staphylococcus aureus (MRSA1 and MRSA2) with MIC (minimum inhibitory concentration) values < 40 pg/mL (see Table). For comparison, vancomycin has an MIC of 2 pg/mL vs. MRSA isolates, 4 and teicoplanin has an MIC of 8 pglmL vs. VRE isolates. 5 In our study, both Gram positive and Gram negative bacteria were tested. However, Gram negative bacteria were only marginally affected by 1. For example, with E. coli ATCC 25922, the MIC value was 160 pg/mL. MIC values were also obtained for 3a, 8-di (3-methyl-2-butenyl)-l-formyl-l,2,3,3a,8,8ahexahydropyrrolo[2,3-b]indole, 2. 6 At up to 320 pg/mL, compound 2 had no effect on the growth of both Gram positive and Gram negative bacteria. The only conclusion that may be drawn from this data is that the antibacterial potency of I depends on the nature of N-1 and/or N-8 substitution and is not simply a function of having a 1,2,3,3a,8,8a-hexahydropyrrolo[2,3-b]indole skeleton with a 3-methyl-2-butenyl group at C-3a.