Lasubines structure

Some data for several L. a. are given in the table. The lythrancines I-Vll belong to structural type 4, lyth-rine, (-)-decinine, and decodine to structural type 2. For the synthesis of lasubines (structural type 1), see Ut. ... 

Fuji et al. (16) have recently isolated lasubine-I (64b) and lasubine-II (63b) from Lagerstroemia subcostata Koehne. The structures of these alkaloids have been established by correlation with synthetic compounds (63a and 64a) as well as by analysis of IR, PMR, 13C-NMR, and mass spectra. These alkaloids are listed in Table IV (16, 47, 48, 50, 51). 

The structure of these bases has been elucidated by spectroscopic and chemical methods. A basic hydrolysis of both subcosine-I and subcosine-II resulted in 3,4-dimethoxycinnamic acid as well as lasubine-I for 69 and lasubine-II for alkaloid 67. 

Synthesis of (—)-Lasubine II. A reductive desulfonylation with lithium in ammonia is employed in the total synthesis of quinolizidine alkaloid (—)-lasubine II.264 A conjugate addition of methyl (.S )-(2-pipcridyl)acetate to an acetylenic sulfone, followed by lithium diisopropylamide (LDA)-promoted intramolecular acylation is the key step in the preparation of the quinolizine structure of (—)-lasubine II (Eq. 154). 

Figure Structural types of the Lythraceae alkaloids 1 phenyl-quinolizkjinetype (10oH=lasubine 1,10/8H=lasubine II) 2 qui-nolizkSne-biphenyl lactone type (10uH=vertine, 1 -...

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