Yield:-

Reaction Conditions:

Stage #1: rac-Ala-OHwith acetic acid in water;Reflux;
Stage #2: cis,trans-2,5-dimethoxytetrahydrofuran in water; for 4 h;Heating;

Steps:

7

Compound 37 (75 g, 852 mmol) was dissolved in 112 ml of water and added to HOAc (750 ml). The reaction mixture was then heated to reflux and compound 38 (112 g, 852 mmol) was added dropwise. After heating for 4 h, the mixture was cooled and concentrated. The reaction mixture was poured into 1.5 L of water and extracted with ethyl acetate (500 ml×3) and dried over Na₂SO₄. The solvent was removed and the crude product of compound 39 (120 g, purity 83%) was used directly without purification

References:

US2009/257979,2009,A1 Location in patent:Page/Page column 60-61