Solution and Solid Phase Synthesis of Unusual a-Amino Acids From

3.1 Introduction
3.1.1 lsa lation and Biological Activity
P,y-Unsaturated arnino acids, or vinylglycines, are a class of a-amino acids which
have garnered much interest due to both their varied biological activity and as synthetic
intermediates.' Various substituted vinylglycines have ken isolated from naturai sources
and found to possess antimicrobial activity. The first isolates were of 2-methylene-
cyclohept-(4,5 or 6)-ene- 1.3-diglycine 3.1 and p-methylene-L-norvaline 3.2 which were
found in the mushmom Lactariris helvus in 19&I2 and 1967)~~ respectively. In 1968 two
more a,e-unsaturated a-amino acids were isolated €rom the mushroom Bankera
fuligineoalba, L-2-amino-3-hydroxymethyl-3-pentenoic acid 3.3 and L-2-arnino-3-
fomyl-3-pentenoic acid 3.4. Graduaily as more and more a$-unsaturated a-amino acids
were isolated their biological activities were detennined. For example, L-2-arnino-4-
methoxy-tram-3-butenoic acid 3.5 was extracted from Pseudomonas aemginosa5 and is
active as an antibiotic against both gram positive and negative bactena by inhibiting
methionine biosynthesis? Rhizobitoxine, an antirnetabolite isolated from root nodules
induced by Rhizodium japonicum in the soybean Glyine max, was identified as 2-amino-
4-(2-amino-3-hydroxypropoxy)-r+ons-but-3noic acid 3.6.' Rhizobitoxine's activity
occurs through a number of pathways, including the inhibition of the conversion of
methionine into ethylene in plants and by irreversibly inactivating B-cystathionase, a