Asymmetric syntheses of optically active α-amino acids by hydrocyanic acid addition to the optically active Schiff base

Abstract

The syntheses of L(+) and D(−) enantiomers of α-amino acids, norvaline, norleucine, and leucine, as their hydrochloride salts have been achieved in almost 100% optical purity and 40–60% overall yield.

How to build optically active?-amino acids

“…46). Thanks to the use of other chiral auxiliaries, yields and optically purities have been improved (Patel and Worsley, 1969;Phadtare et al, 1985), as previously reviewed (Williams, 1989;Duthaler, 1994).…”

Determination of enantiomeric excess of leucine and valine by X-ray powder diffraction

“…Leucine [1,2] and valine [3,4] are two of the twenty most common amino acids on Earth. Only their L-enantiomers appear in mammalian proteins.…”

The Synthesis of (S)‐(+)‐2‐Amino‐3‐(1‐adamantyl)‐propionic Acid (L‐(+)‐Adamantylalanine, Ada) as a ‘Fat’ or ‘Super’ Analogue of Leucine and Phenylalanine

“…The lower homologue of adamantylalanine, a-amino-(1-adamanty1)-acetic acid, as well as its isomer, a-amino-(2-adamantyl)-acetic acid have been prepared as racemates [6]; they bear no specific resemblance to any natural amino acid. The synthesis was carried out according to the modified Strecker procedure of Patel & WorsZey [7] as shown in the Scheme. Physical and analytical data are displayed in Tables I -7.…”

“…The NMR. assignments are to the protons of: 1 = adamantyl; 2= C(2) (ethane); 3= C( 1); 4= adamantyl+ C(3)+ CH3; 5= C(2) (propionyl); 6= benzyl; 7= phenyl; 8= adamantyl+ C(3); 9=CH3 of BOC; 10= NH of urethane; 11 = COOH (broad signal); 12= 8+ quinine C (2)(3)(4)(5)(6)(7)(8); 13= OCH3 of quinine; 14=C(2)+C (9) chirality, e.g. aspartic acid.…”

“…aspartic acid. Three h e s of circumstantial evidence point to the S-or natural L-configuration of 6: The first is the observation of Pate1 & Wordey [7] that the use of (S)-(-)-a-methylbenzylamine led to the production of the natural amino acids with usually more than 90% optical purity in all of their experiments. A priori there is no reason to expect our case to be an exception.…”