Montanine type alkaloids

Fig. 22 Chemo-enzymatic, enantio-selective total synthesis of three non-natural montanine type alkaloids, (+)-brunsvigine, (+)-nangustine and (+)-montabuphine (TD toluene dioxygenase)...

Galanthamine-type alkaloids derived from a dibenzofuran ring Crinine-type alkaloids derived from 5,10b-ethanophenanthridine Montanine-type alkaloids derived from 5, 11b-... 

Although synthetic approaches toward the montanine-type alkaloids had been made by intramolecular cyclization of 3-(3,4-methylenedioxy)phenyl-hexahydroindoline derivatives (176), these attempts were thus far unsuccessful. The 5,11-methanomorphanthridine ring systems 341-343 (Fig. 21)... 

The montanine-type alkaloids, also deriving from the hemanthamine series, are very unusual. Only two, namely pancracine (73) and nangustine (74), have been isolated from two species, both belonging to the Narcissus section of this genus. Nangustine has a unique substitution pattern (80), being the first 5,11-methanomorphanthridine alkaloid with a C-3/C-4 substitution, instead of a typical C-2/C-3. 

There is little information about the montanine-type alkaloids, only some data about pancracine (73), which shows antibacterial activity against S. aureus and Pseudomonas aerogitwsa (326), as well as weak activity against Tripanosoma brucei rhodesiense, T. cruzi, and P. falciparum (80). 

Montanine-type alkaloids constitute a limited group in Amaryllidaceae alkaloids and show a characteristic 5,11-methanomorphanthridine framework (Table 17.7). There are two classes of C = C double bond substitution patterns in the C ring of alkaloid skeletons. Alkaloid nangustine 151 is the first member in this subgroup with a hydroxyl group at the C4 [42]. 

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