Mushroom amino acid synthesis

In 1972 Bayer and Kneifel isolated (98) a pale blue compound from A. muscaria containing vanadium, which they named amavadine. They proposed (98,99) that it consisted of a complex of AT-hydroxyimino-a,a -dipropionic acid with in a 2 1 ratio. From a comparison of the EPR spectra of segments of frozen mushrooms with those of vanadyl complexes of various amino acids, it was concluded (100,101) that this proposal was not very likely. However, Krauss et al. (102) synthesized amavadine and compared its EPR properties with the complex extracted from the mushroom and concluded that it was the same. Others were unable to reproduce the synthesis (103), although models analogous to amavadine were reported. The synthesis of the ligand N-hydroxy-a,a -iminodipropionic acid, and related compounds was, however, later confirmed (104-106). The stereochemistry and total synthesis of the vanadium compound of A. muscaria has now been elucidated (107). 

The desire to produce enantiomerically pure pharmaceuticals and other fine chemicals has advanced the field of asymmetric catalytic technologies. Since the independent discoveries of Knowles and Homer [1,2] the number of innovative asymmetric catalysis for hydrogenation and other reactions has mushroomed. Initially, nature was the sole provider of enantiomeric and diastereoisomeric compounds these form what is known as the chiral pool. This pool is comprised of relatively inexpensive, readily available, optically active natural products, such as carbohydrates, hydroxy acids, and amino acids, that can be used as starting materials for asymmetric synthesis [3,4]. Before 1968, early attempts to mimic nature s biocatalysis through noble metal asymmetric catalysis primarily focused on a heterogeneous catalyst that used chiral supports [5] such as quartz, natural fibers, and polypeptides. An alternative strategy was hydrogenation of substrates modified by a chiral auxiliary [6]. 

Vinylglycine is a natural amino acid found in mushrooms. It is an inhibitor of pyridoxai-linked aspartate aminotransferase, and has also been postulated as an intermediate in the enzymatic conversion of homoserine to threonine and o-ketobutyrate. Protected vinylglycine is also a versatile asymmetric starting material for synthesis.7 Variants have been prepared in racemic. " optically active, optically pure,2.15-17 and isotopically labeled form.4b.i8-20 xhis procedure is derived from our earlier publication and contains improvements in procedure and scale-up. 

A new, more convenient route to a-hydroxymethylserine has been developed, and a method for the synthesis of l-amino-2-arylcyclopropanecarboxylic acids (173) from aryl aldehydes and iV-benzylthiothiocarbonylglycine has been repor-ted, as well as a total synthesis of coprine (174), the disulphiram-like principle of the inky cap mushroom. 5-(2-Carboxypropyl)-L-cysteine (175), a component of... 

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