Nonproteinogenic amino acids, syntheses

Formation of functionalized cyclic nitrones via a new reaction intermediate, nitrosoketene, and its development for the synthesis of nonproteinogenic amino acids 99YGK116. 

Schollkopf, U. Enantioselective Synthesis of Nonproteinogenic Amino Acids. 109, 65-84 (1983). 

In the search of new methodologies for the asymmetric synthesis of nonproteinogenic amino acids, 8-methyl-4,8a-diphenyltetrahydro-17/-pyrrolo[2.1 -r l, 4 oxazinc-l, 6(7//)-dionc 62, obtained as described in Scheme 24 (Section 11.11.7.3), was selectively reduced at the lactam carbonyl with BH3 and further opened by hydrogenolysis to give syn-disubstituted proline derivative 64 in 95% yield <1997SL935> (Scheme 6). It is noteworthy that hydrogenolysis did not affect the benzylic position of bicyclic compound 63. 

Schollkopf, U. Enantioselective Synthesis of Nonproteinogenic Amino Acids. 109, 65-84 (1983). Shibata, M. Modern Syntheses of Cobalt(III) Complexes. 110, 1-120 (1983). ... 

The Strecker amino acid synthesis, which involves treatment of aldehydes with ammonia and hydrogen cyanide (or equivalents) followed by hydrolysis of the intermediate a-amino nitriles to provide a-amino acids (Scheme 1), was first reported in 1850 [1], This method has been applied on an industrial scale toward the synthesis of racemic a-amino acids, but more recently interest in nonproteinogenic a-amino acids in a variety of scientific disciplines has prompted intense activity in the asymmetric syntheses of a-amino acids [2]. The catalytic asymmetric Strecker-type reaction offers one of the most direct and viable methods for the asymmetric synthesis of a-amino acid derivatives. It is the purpose of this Highlight to disclose recent developments in this emerging field of importance. 

This chapter reviews recent developments in the synthesis of both naturally occurring and unnatural acromelic acids, important members of the kainoid class of neuroexcitatory nonproteinogenic amino acid. 

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