| asymmetric total synthesis of dendrobatid alkaloids: preparation of indolizidine 251f and its 3-desmethyl analogue using an intramolecular schmidt reaction strategy. | total syntheses of alkaloid 251f (1), a natural product detected from the skin extracts of the dendrobatid frog species minyobates bombetes, and its racemic 3-desmethyl derivative (2) are reported. a diels-alder reaction initiated both syntheses and established four consecutive stereogenic centers. important to the synthesis of 2 was a first-generation ozonolysis/olefination/aldol strategy to convert a [2.2.1] bicyclic acid to the [3.3.0]bicyclooctane diquinane 4b. further elaboration to an appr ... | 2004 | 15113219 |
| a new class of alkaloids from a dendrobatid poison frog: a structure for alkaloid 251f. | alkaloids of a new class are present in skin extracts of the dendrobatid poison frog, minyobates bombetes, of colombia. the structure of the major alkaloid of this class, 251f, has been determined as a trimethylcyclopenta[b]quinolizidinemethanol 1 by nmr, gc-ft-ir, and ms studies including ms-ms. at least nine congeners of 251f were detected in these extracts. | 1992 | 1522417 |