Editing Synthesis-of-dendritic-lipid (section)

== Synthesis of&nbsp;Nα,Nδ-bis(tert-Butyl-carbamoyl)ornithine ==

<span style="line-height: 20.8px;">Over the course of 1 hour, 25 ml of 4 M NaOH and&nbsp;</span>&nbsp;a solution of 27.3 g (125 mmol) Boc2O (Novabiochem) in THF were added to a solution of&nbsp;9.15 g (54.3 mmol) L-ornithine hydrochlorite (Aldrich) and 30 ml 4 M NaOH in 250 ml water in four portions.

<span style="line-height: 20.8px;">&nbsp;L-ornithine hydrochlorite:&nbsp;</span>VWR: $92.77/100g A12111-22

Di-tert-butyl dicarbonate ,&nbsp;<span style="line-height: 20.8px;">Boc2O, VWR/</span>Alfa Aesar Di-tert-butyl dicarbonate $119.44/100g

After stirring for 3 hour at room temperature, the THF was evaporated.

Following the addition of 100 ml of ethyl acetate, the resulting mixture was acidified using half-concentrated HCl (about 60 ml).

The phases were separated, and the aqueous phase were extracted two more times with 100 ml of EtAc each

The combined organic phases were washed twice with 200 ml of water, dried (Na2SO4) and evaporated.

The residue was dissolved in little EtAc, and 600 ml of cyclohexane were added.

After standing at room temperature for 14 hours, the mixture was filtered, and the residue was washed with cyclohexane and dried to yield 16.6 g (49.9 mmol, 92%) of Boc2Orn as colorless crystals.