Why protect: heat two amino acidsHeat two amino acids and water leaves between an acid and an amine. Draw what forms, and count how little of it is the peptide you wanted.

The dipeptide you hope for: Heat glycine and alanine together, and water leaves between an acid and an amine. Draw the dipeptide in which glycine’s acid is bonded to alanine’s amine.

Heat does not choose: Nothing tells glycine’s acid to react with alanine rather than with another glycine. Draw the three other dipeptides the same flask holds.

Two stereocentres: With phenylalanine and alanine, each dipeptide carries two stereocentres. Draw both mixed dipeptides, each α-carbon in its natural configuration.

And the chains grow on: Every dipeptide still has a free amine and a free acid, so it reacts again. Draw two of the tripeptides HGlyAlaOH grows into.

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

Our other tools

learn.cheminfo.org — Arrange the tools into a course and hand out its link.

inchi.cheminfo.org — InChI and InChIKey from a structure, in the browser.

vcl.cheminfo.org — Combine a core and fragments into a screened library.

smiles.cheminfo.org — Draw a structure, read its SMILES, learn the notation.

iupac-name.cheminfo.org — The IUPAC name of a structure, and the structure a name denotes.

openbabel.cheminfo.org — Convert a structure between any pair of chemical file formats.

www.chemcalc.org — Molecular formula, exact mass and isotopic distribution.

dbe.cheminfo.org — Count rings and double bonds from a formula or a structure.

metabo.nmrium.com — Turn a batch of NMR spectra into a map of your samples.

derepflow.cheminfo.org — Identify the constituents of a mixture from its ¹³C spectrum.

isomers.cheminfo.org — Every constitutional isomer of a molecular formula.

tex.cheminfo.org — Write LaTeX and mhchem formulas, and save them as SVG.

lcao.cheminfo.org — Combine atomic orbitals into molecular ones.

regexp.cheminfo.org — Learn regular expressions in a live playground.

pdb.cheminfo.org — A fast look at any Protein Data Bank entry.

elucidation.cheminfo.org — A structure from a 1H NMR spectrum and a formula.

spectroscopy.cheminfo.org — Find a structure from its IR, mass and NMR spectra.

equilibrium.cheminfo.org — Chemical equilibria: pH, speciation and titration curves.

polycarp.cheminfo.org — Predict the microstructure of a radical copolymerisation.

3d.cheminfo.org — Conformers in 3D from a structure you draw.

periodic-table.cheminfo.org — The periodic table, coloured, plotted and taken apart.

database.cheminfo.org — Query a real chemical dataset in SQL and in Mango.

chembio.cheminfo.org — Natural products, and the organisms they were found in.

wikidata.cheminfo.org — The chemistry of Wikipedia’s infoboxes, searchable by structure.

symmetry.cheminfo.org — Find the symmetry of a molecule, a crystal or a pattern.

osiris.cheminfo.org — Predicted toxicity risks and properties, one molecule or many.

atoms.cheminfo.org — Electrons, neutrons, Lewis structures and oxidation states.

moles.cheminfo.org — Balance a reaction, and work out its mass composition.

inorganic.cheminfo.org — Name an inorganic compound, and write its formula.

slides.cheminfo.org — Put a live tool on a slide, from the link its Share button gives.

vibrations.cheminfo.org — IR and Raman spectra computed in the browser.

draw.cheminfo.org — Journal-grade structures, in an SVG that keeps the chemistry.

plate.cheminfo.org — Read a TLC plate, a gel or a blot from a photograph.

glassware.cheminfo.org — Assemble lab glassware into a working apparatus, and draw it.

write.cheminfo.org — Write documents holding structures, 3D models and plates that open again where they were made.