Cryptostyline alkaloids

The number of alkaloids based on the 1-substituted tetrahydroisoquinoline skeleton is legion and the structural variation which this skeleton affords, particularly in the case of 1-benzylisoquinolines, is rich. The 1-substituted isoquinoline skeleton of each kind probably arises by the common step of condensing a j8-arylethylamine with an appropriate carbonyl compound, for which the Pictet-Spengler reaction provides an analogy. In some cases the participation of a carbonyl compound is established but in others it is still speculative. Recently progress has been made in this area in studies on the biosynthesis of lophocerine, the Papaver alkaloids, and to some extent the cryptostyline alkaloids with their novel 1-phenylisoquinoline structures. 

Dimers and Oligomers of Isoquinoline Alkaloids Cryptostyline Alkaloids Distribution of Isoquinoline Alkaloids Biological Activity... 

Fig. 32.4. Proposed biosynthesis of cryptostyline alkaloids (modified from Lundstrom, 1983 used with permission of the copyright owner. Academic...

There are only two groups of alkaloids that appear to be derived from tyrosine (25, R = OH) utilized as a Cg—C2 fragment and a Cg—Cj unit which comes from phenylalanine (25, R = H). The first is that small group found only in the Orchidaceae, exemplified by cryptostyline I [22324-79-4] (67, from Cryptostylisfulva Schltri) C29H22NO4. 

Both dopamine and vanillin (but not isovanillin) serve as precursors for the remaining Ce-Cj residue in cryptostyline-I. The incorporation of vanillin was at a low level, but this was attributed to poor absorption into the plant. Protocatechual-dehyde, the known precursor for the Q-Ci unit found in the Amaryllidaceae alkaloids, has not yet been tested as as a precursor. 

Phenyltetrahydroisoquinoline alkaloids. Rare structures that only occur in orchids (Orchidaceae), e. g., cryptostyline I C 9H2,n04, Mr 327.4, mp. 101-102°C, [aJo +56° (CHCI3) from Cryptostylis... 

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