Leucine or Isoleucine? That is the Question...

Leucine and isoleucine are two very similar amino acids with the only structural difference in the positioning of a methyl group on the carbon chain. However, there are substantial differences. The properties of these two amino acids are summed up in the description below. After reviewing this post, if you are confronted with these two amino acids, you should be able and equipped to answer the opening question, "Leucine or Isoleucine?"

Leucine^1,2

Three Letter Representation: Leu

Two Letter Representation: L

IUPAC Name: (2S)-2-amino-4-methylpentanoic acid

Formula: C₆H₁₃NO₂

Molecular Weight: 131.2

Acidic, Neutral, or Basic: Neutral

pKas: For α-COOH = 2.33, for β-NH₃⁺ = 9.74

pI: 6.04

Isoleucine^1,2

Three Letter Representation: Ile

Two Letter Representation: I

IUPAC Name: (2S,3S)-2-amino-3-methylpentanoic acid

Formula: C₆H₁₃NO₂

Molecular Weight: 131.2

Acidic, Neutral, or Basic: Neutral

pKas: For α-COOH = 2.32, for β-NH₃⁺ = 9.76

pI: 6.04

Structures of these amino acids are given below. On ball and stick representations, only hydrogens on stereogenic carbons are shown.

References:

1) Smith, J. Organic Chemistry, 3rd ed.; McGraw-Hill: New York, 2011; 1076

2) Smith, J. Organic Chemistry, 3rd ed.; McGraw-Hill: New York, 2011; 1078

3)  ACD ChemSketch, version 2009; Advanced Chemistry Development, Inc.; (Accessed March 2, 2013).

Sick Again? Oh Dear! Get Oseltamivir!

~If you’re like so many who are sick with the flu, then perhaps some Oseltamivir is for you!~

Oseltamivir, or more commonly known as Tamiflu®, is a commonly prescribed antiviral drug used mostly in the prevention and treatment of certain cases of influenza.¹ Though Oseltamivir’s trade name is Tamiflu®, its IUPAC formal name is:

ethyl (3R,4R,5S)-4-(acetylamino)-5-amino-3-(pentan-3-yloxy)cyclohex-1-ene-1-carboxylate. ²

Though there are several methods to synthesize Oseltamivir, the reaction scheme shown below highlights the implementation of a Diels-Alder, or pericyclic, reaction in the first step.³ (Emphasis on the Diels-Alder reaction with the yellow highlight box was added by the blog author).

...and now you know. Next time you have the flu, you may just have to take time and pay your respects to the Diels-Alder Reaction.

References:

1) Mayo Clinic. Oseltamivir (Oral Route) <http://www.mayoclinic.com/health/drug-information/DR601671> (Accessed Feb 11, 2013).

2) ACD ChemSketch, version 2009; Advanced Chemistry Development, Inc.; (Accessed Feb 11, 2013).

3) SynArchive.com: The Organic Synthesis Archive. Oseltamivir. <http://www.synarchive.com/syn/149> (Accessed Feb 11, 2013).