Synthesis of Amino Acids

Strecker synthesis builds an alpha-amino acid from an aldehyde + ammonium chloride (NH3 source) + potassium cyanide, across 2 steps: (1) form an alpha-aminonitrile via imine formation then cyanide attack, (2) acid-catalyzed hydrolysis of the nitrile to the final amino acid.
Gabriel synthesis (formally N-phthalimidomalonic ester synthesis) starts from potassium phthalimide + diethyl bromomalonate: SN2 amination → deprotonation/alkylation with R-Br installs the side chain → base hydrolysis opens phthalimide/esters → acid-catalyzed decarboxylation yields the amino acid.
Both syntheses produce racemic mixtures (equal L/D) because they proceed through planar (sp2) intermediates that nucleophiles can attack from either face with equal probability — no stereochemical control.

1Step 1a: Acid protonates the aldehyde's carbonyl oxygen, increasing carbonyl carbon electrophilicity.
2Step 1b: Ammonia attacks the carbonyl carbon; proton transfer + water elimination converts it to an imine (C=N).
3Step 1c: Cyanide ion attacks the imine carbon, breaking C=N and forming a nitrile — yields the alpha-aminonitrile intermediate.
4Step 2a: Under acid, the nitrile nitrogen is protonated, increasing nitrile carbon electrophilicity.
5Step 2b: Water attacks the nitrile carbon, opening the triple bond; proton transfers/rearrangements complete conversion to the carboxyl group — yields the final alpha-amino acid.

1Step 1: SN2 amination — phthalimide's nitrogen (nucleophile) displaces bromide on diethyl bromomalonate, forming the N-phthalimidomalonic ester intermediate.
2Step 2: Strong base deprotonates the central carbon between the two ester groups, forming a carbanion, which undergoes a second SN2 with an alkyl halide (R-Br) to install the side chain.
3Steps 3-4: Aqueous base + heat hydrolyzes the phthalimide ring and ester groups (esters → carboxylic acids, free amine released); acid + heat then drives decarboxylation (loses CO2) to yield the final alpha-amino acid.

Feature	Comparison
Starting materials	Strecker: aldehyde + NH4Cl + KCN. Gabriel: potassium phthalimide + diethyl bromomalonate + R-Br.
Key intermediate	Strecker: alpha-aminonitrile. Gabriel: N-phthalimidomalonic ester → carbanion → alkylated diester.
Final step	Strecker: acid-catalyzed hydrolysis of nitrile → COOH. Gabriel: acid-catalyzed decarboxylation (loses CO2).
Stereochemical outcome	Both racemic — planar intermediates allow attack from either face equally.

Both syntheses are racemic for the SAME underlying reason (planar sp2 intermediate, no facial selectivity) — don't invent different explanations for each.
Gabriel synthesis's final step is decarboxylation (loses CO2), not another hydrolysis — hydrolysis (steps 3-4a) happens first to free the amine and convert esters to carboxylic acids; decarboxylation is the separate, final step.
"Gabriel synthesis" and "malonic ester synthesis" are being used informally as the same combined method here (more precisely N-phthalimidomalonic ester synthesis) — don't treat them as two separate named reactions when applied to amino acid synthesis.

What three reagents start the Strecker synthesis, and what is the Step 1 product called?

Why do both the Strecker and Gabriel syntheses produce racemic amino acid mixtures?

What is the final step of the Gabriel synthesis, and what does it remove?

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