Catharanthus Alkaloids XXXIII. 21'-Oxo-Leurosine From Catharanthus Roseus (Apocynaceae)

Microbial Transformations of Natural Antitumor Agents. 16. Conversion of Leurosine to 10'-Hydroxyleurosine by Streptomyces Species

“…2.70 (s, 3H, -NCHs), 3.61 (s, 3H, 16'-C02CH3), 3.79, 3.81 (2s, 6H, 16-CO,CH3 and ll-OCH3), 5.28 (d, 1H, 15-H), 5.43 (s, 1H, 17-H), 5.83 (m, 1H, 14-H), 6.09 (s, 1H, 12-H), 6.57 (s, 1H, 9-H), 7.11 (m, 3H, 10', 111 and 12'-H), 7.49 (d, 1H, 9'-H) and 7.97 (s, 1H, indole N-H). These data correspond well with published properties for leurosine (3,(6)(7)(8)(9)(10) and related alkaloids (11,12).…”

Structure elucidation of indole–indoline type alkaloids: A retrospective account from the point of view of current NMR and MS technology

“…In this case, besides the molecular ion peak a mass shift of 2 Da could be observed for the transmethylated vindoline moiety and its fragments, such as m/z 124, while the velbanamine moiety remained intact (fragments B and D). Similarly, comparison of the EI-MS fragmentation of C(21 )-oxo-leurosine [26] to that of leurosine suggested that the oxo function was located on the velbanamine half of the molecule.…”

“…Since LEU was derived from VLB, and VLB has a C(20 )-␤-OH group, it was incorrectly suggested as a seemingly plausible scenario that in LEU the epoxy-ring bridging the C(15 ) C(20 ) moiety was in the ␤ position [20]. Making use of the spectral data observed for LEU, on the basis of low-resolution 1 H and 13 C NMR data the structure of C(21 )-oxo-LEU was described improperly [26] as well. The correct ␣-stereoposition of the epoxy-ring in LEU was determined in 1981 [60].…”

Catharanthus Alkaloids XXXVII. 16-Epi-Z-Isositsirikine, a Monomeric Indole Alkaloid with Antineoplastic Activity from Catharanthus roseus and Rhazya stricta

“…NaBH4 reduction of geissoschizine (2).-To a solution of geissoschizine (2, 2 mg) in methanol (5 ml), NaBh4 was added and the mixture kept at room temperature overnight. After the usual work-up, the reaction mixture displayed two spots under the solvent system chloroform-methanol (95:5) on silica gel, eluting twice.…”