NALPHA-FMOC-L-SERINE TERT-BUTYL ESTER

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Nα-(Fluoren-9-ylmethoxycarbonyl)-3-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-α-D-galactopyranosyl)-L-serine tert-butyl ester 1 was prepared as previously described (Lemieux et al (1979), Ferrari et al. (1980)) by glycosylation of Nα-(Fluoren-9-ylmethoxycarbonyl)-L-serine tert-butyl ester (Vowimkel et al. (1967) Schultz et al. (1993)) with 3,4,6-tri-O-acetyl-2-azido-2-deoxy-p-D-galactopyranosyl chloride (obtained from tri-O-acetyl-D-galactal) (Shafizadseh et al. (1963)) using AgOTf as catalysts, followed by the reduction and acetylation of the 2-position (Paulsen et al. (1982)). The t-butyl ester of 1 (2 g, 2.8 mmol) was then deprotected in formic acid (76 ml) (Paulsen et al. (1989)). The solution was stirred for 10 h and evaporated. The residue was dissolved in MeOH (200 ml) and the acetyl groups of the sugar moiety were removed by adding, dropwise, a solution of 1% MeONa (pH 11) (Meinjohanns et al. (1995)). After 15 h, the medium was neutralized by a Dowex 50WX8 (H+) resin and the final product 2 purified on a reverse phase column (C18) using a gradient of water/MeCN 1.27 g (yield 79%). evaporated The residue was dissolved in MeOH (200 ml) the acetyl groups of the sugar moiety were removed by adding After 15 h the final product 2 purified on a reverse phase column (C18)