Awhile back, I discussed dicyclohexylcarbodiimide: a condensing agent that helps turn biological monomers (like amino acids) into polymers (like proteins). People use it a lot on peptide synthesizers for this purpose, where the peptides are made in organic solvents. A related compound, EDAC, works in water:
EDAC works just like dicyclohexylcarbodiimide, but in water. People have used it to, for example, condense short pieces of DNA into longer ones.
I’ve heard it’s a sensitizer (allergen) like DCC, but I’m not sure if it’s quite as bad (no vapor pressure, anyway).