<jats:title>Abstract</jats:title> <jats:p> From the culture medium of Pseudomonas putida several derivatives of 3,4-dihydro-5-methyl- 2H-pyrrole were isolated differing in the C-4 substituent (unbranched C<jats:sub>11</jats:sub>, C<jats:sub>13</jats:sub> and C<jats:sub>15</jats:sub> alkyl and alkenyl groups), the structures of which could be elucidated