Structure Elucidation and Spectroscopy

The almost simultaneous discovery of vinblastine (1) by Noble et al. (57) and by Svoboda and co-workers (58) is one of the the most publicized events in alkaloid chemistry. Since its initial discovery, vinblastine (1) has been reisolated from C. roseus several times (47 9,57-60,) and it has also obtained from C. ovalis (32), C. longifolius (33), and C. trichophyllus (60). The large-scale separation of vinblastine (1) and vincristine (2) from C. roseus received attention from pharmaceutical industries, and several procedures for the separation of these alkaloids have been reported in the patent literature (61-71). 

The initial structure elucidation of vinblastine (1) has been reviewed (1,3) however, the complete assignment of its H- and C-NMR spectra was made possible only by recent developments in high-resolution NMR spectroscopy. An extensive H-NMR study on vinblastine (1) has appeared (72) (Table III), reporting the H-NMR data of 1 in CDC1  

The absolute configuration of the stereo centers of vinblastine (1) was determined from the X-ray crystal structure of vincristine (2) methiodide (79,80) in view of the known relationship between 1 and 2. The absolute stereochemistry at C-I8 in vinblastine (1) and related derivatives can also be deduced by means of ORD and CD spectroscopy (81,82). The determination was made possible by the synthesis and structure elucidation of several compounds possessing the unnatural configuration at C-18 (82,84). Because this stereo center controls the relative geometry of the 

Deacetoxyvinblastine (5) (formerly named desacetoxyvincaleukoblas-tine), C46H56N4O7, mp I83-190°C, was first isolated by Neuss et al. 35) in the course of purifying quantities of vinblastine (I) obtained from C. roseus. Recently, 5 was reisolated, and a thorough H-NMR study was performed in order to establish its structure. The lack of an acetate 

Demethylvinblastine (7) (formerly named N-desmethylvincaleukoblas-tine and A -deformyl-vincristine), C45H56N4O9, mp 250°C (sulfate salt), has 

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