Coupling: activate the acid with DCCAn acid and an amine make a salt, not an amide. DCC turns the acid into an O-acylisourea that the amine attacks; draw each piece.

An acid and an amine make a salt: Mix a protected acid and a protected amine at room temperature, with no reagent. A proton moves before any bond forms: draw the salt.

DCC activates the acid: DCC, N,N’-dicyclohexylcarbodiimide, turns the OH of an acid into a group that leaves easily. Draw the activated acid it makes from BocGlyOH.

The amine attacks the activated acid: The O-acylisourea is an acid with a good leaving group in place of its OH. Draw the intermediate, the dipeptide and the urea left from DCC.

The same coupling, Cbz and methyl ester: DCC couples any N-protected acid with any C-protected amine. Draw the activated acid, the dipeptide and the urea for CbzPheOH and HGlyOMe.

DCC with nothing protected: Glycine carries a free amine and a free acid, and DCC activates any acid it meets. Draw what it makes from glycine alone.

Draw the products and intermediates of a peptide synthesis, from protecting groups to DCC coupling, and follow two slide shows. The exercises need JavaScript, because every drawing is checked in your browser.

Why protect — heat two amino acids, and count what forms

Protecting groups — put them on, take them off

Coupling with DCC — activate the acid, then form the amide

Planning a synthesis — protect, couple, deprotect, in the right order

Builder — type a sequence, see the molecule

Cheatsheet — every group, how it goes on and comes off

Talks — two slide shows, mechanisms included

About — what the site is, and how to cite it

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