Sometimes chemists need the unnatural D enantiomer of an amino acid, often as part of a drug or an insecticide. Most L-amino acids are isolated from proteins, but the D-amino acids are rarely found in natural proteins. D-amino acids can be synthesized from the corresponding L-amino acids. The following synthetic scheme is one of the possible methods.

(a) Draw the structures of intermediates 1 and 2 in this scheme.
(b) How do we know that the product is entirely the unnatural D configuration?

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COOH COOH NaN, intermediate 2- H2 R -HCI, intermediate l NaN3 → R HC pR NH2 D configuration L configuration