GROUP-ASSISTED PURIFICATION (GAP) FOR PROTECTION OF AMINO ACIDS USING N-PHOSPHONYL FUNCTIONAL GROUPS (Dedicated to Professor Isao Kuwajima on the occasion of his 77th birthday)

General The 1 H NMR, 13 C NMR and 31 P NMR spectra were recorded on a Jeol eclipse 400 SS (operating at 400 MHz for proton) at ambient temperature. The ESI-MS and ESI-HRMS were recorded with an Exactive (Thermo Scientific, San Jose, CA) mass spectrometer. Dry dichloromethane (DCM) was bought from Acros Organics and used directly. N, N’dimethylformamide (DMF) was dried over 4 Å molecule sieves powder. 4Ǻ molecular sieves powder was activated by heating in oven at 120 o C for 24 hours. Triethylamine was stand over KOH solid overnight and distilled before use. Tetrahedron furan (THF) was distilled from Na metal before use. All the other chemicals were bought from commercial source and used directly after arrival.