http://www.pepnet.com/hctureagent.html
http://www.pepnet.com/images/HCTU.jpg
inexpensive, little racemization, non-toxic, non-irritant, stable...
A key element for developing a new condensing agent is the resulting stereochemistry of the amino acid; it is critical to maintain chiral integrity during chain elongation. Incorporation of a better leaving group during amide bond formation can lead to racemization of the alpha-carbon due to its increased acidity which promotes enolization and oxazolone formation during the activation step (2). Recently at the European Peptide Symposium Di Fenza and Rovero reported reduced rates of racemization when HCTU was used as the coupling reagent as compared to BOP. Overall, HCTU is an excellent, new coupling reagent that offers high yields and low levels of racemization.
- - says the manufacturer - -
this would be good for our favorite lysergic conversion due to the chiral importance of that 8 position, no?
so, i cut this from
https://www.thevespiary.org/rhodium/Rhodium/chemistry/lsd.coupling.agents.html
Proposed LSD synthesis procedure:
1eq. LSA is dissolved in a suitable solvent(must be fairly dry) at RT, 1.05 eq HBTU/HATU is added. 2eq. of diethylamine is added and the rxn is stirred at RT until it goes to completion (15min-2hr). The solvent is removed under vacuum and the residue partitioned between EtOAc (or other suitable solvent) and saturated NaHCO3 (or NH4OH). The layers were separated and the organics were washed with NaHCO3 (or NH4OH), H2O, saturated NaCl, dried over MgSO4, filtered and concentrated in vacuo to remove the solvent and excess diethylamine. The crude LSD, which should be fairly pure, is then further purified by chromatography and converted to the tartrate salt.
now, if i suppose correctly, hctu can be used in its place... does anyone see any problems there?
at $125usd/100g it is not so expensive...
oops, my brother wants his computer back so i have to leave this thought unfinished. i was in the middle of doing a weight-cost analysis for the chems involved in a hctu lsd synth from lsa...