Dry methanol

The residual moisture content of the freeze-dried product obtained from the model validation runs, was determined using Karl Fischer titration as described by Hansen et al. [29] . The freeze-dried product was reconstituted with a known volume of dry methanol (Sigma-Aldrich, Saint Louis, MO, USA) and left to equilibrate for roughly 15 minutes. With the help of a syringe, a known volume of this solution was volumetrically removed from the vial, injected in the titration vessel of the Mettler Toledo V30 volumetric Karl Fischer titrator (Schwerzenbach, Switzerland) and titrated with Hydranal R titration solvent (Sigma-Aldrich, Saint Louis, MO, USA). Prior to the measurement of the residual water, the moisture content of the dry methanol was determined in triplicate and subtracted from the result. The residual moisture content of the freeze-dried product was determined for three different validation runs.

Dichloromethane was dried by heating under reflux over CaH 2 and distilled under an atmosphere of nitrogen. Tetrahydrofuran was dried by heating under reflux with sodium/benzophenone under a nitrogen atmosphere and collected by distillation. Dry 1,4-dioxane and dry methanol were purchased from Sigma-Aldrich and Acros Organics, respectively. Reagents were purchased at the highest commercial quality and were used as received without further purification.
Yields refer to chromatographically and spectroscopically ( 1 H NMR) homogeneous material, unless otherwise stated.
Reactions were monitored on an Agilent 1200 series HPLC system fitted with an Ascentis® Express C18-column (2.7 µm particle size, 4.6 mm internal diameter), using acetonitrile/water The enantiomeric excess (ee) of chiral compounds was determined via chiral HPLC analysis using a Daicel Chiralpak IA column (5 µm particle size, 150 mm length, 2.1 mm internal diameter). Detection wavelengths were set at 268, 234 and 296 nm. Analyses under reversed phase and normal phase conditions were performed at 25 °C and 35 °C, respectively. Optical rotations were obtained on a Jasco P-2000 polarimeter and are reported in deg mL g -1 dm -1 ; concentrations are reported in grams per 100 mL.