Boehmeria platyphylla

The intermediate diarylquinolizidinone (40) was also reduced by means of lithium aluminium hydride to give the related tertiary amine (44), which was shown to be identical with the seco-phenanthroquinolizidine alkaloid isolated from Boehmeria platyphylla Don. ° The identity of the synthetic material with the natural base, for which [a]o +4.6° was reported, suggests that the latter is largely racemic. ... 

Aphananthe philippinensis Planchon Boehmeria platyphylla Don Cypholophus decipiens H. Winkler C. friesianus (K. Schum.) H. Winkler Cypholophus sp. 

Phenanthroindolizidine and phenanthroquinolizidine alkaloids have similar pentacyclic structures however, the latter compounds contain a 6-membered piperidine E ring rather than the 5-membered pyrrolidine E ring found in the former compounds. Cryptopleurine (5), Fig. (2), is a representative and important phenanthroquinolizidine alkaloid. It is isolated primarily from Cryptocarya pleurosperma [20], but also from Cryptocarya laevigata [21], Boehmeria cylindrica [22, 23], Boehmeria platyphylla [24], Boehmeria caudate [21], and Cissus rheifolia [25], and is known as a highly toxic skin irritant and vesicant. 

Method 6. This synthesis is biomimetic (52), and the product of the first reaction, 33, occurs naturally along with oyptopleurine (18) in Boehmeria platyphylla and B. cylindrica (26,27). The penultimate stage is the alkaloid julandine (24), which also occurs in these two plants (26,27). The synthesis can be modified (52) to afford tylophorine (13) through the secophenanthro-indolizidine alkaloid septidne (30) (27,33,56). 

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