The structures of five new alkaloids have been established: the isoprosopinines A and B, 1 and 2 are homogeneous mixture: isoprosopinine A is (2R, 3S, 6R) 2‐hydroxymethyl 3‐hydroxy 6‐dodecyl 7°‐keto piperidine and isoprosopinine B is (2R, 3S, 6R) 2‐hydroxymethyl 3‐hydroxy 6‐dodecyl 8°‐keto piperidine. Prosophylline 4 is d 2‐hydroxymethyl 3‐hydroxyl 6‐dodecyl 10°‐keto piperidine, prosafrine 9 is (2R, 3R, 6S) 2‐methyl 3‐hydroxy 6‐dodecyl 10°‐hydroxy piperidine and prosafrinine 11, is (2R, 3R, 6S) 2‐methyl 3‐hydroxy 6‐dodecyl 10°‐keto piperidine. Copyright © 1972 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim