Yield:476371-85-4 47.3%

Reaction Conditions:

with trifluoroacetic acid in pentane at 55; for 48 h;Inert atmosphere;

Steps:

5.A

To a flame dried flask under Ar atmosphere was charged with (S)-thiolactic acid (4.17 g, 39.3 mmol), followed by pentane (80 mL) and pivaladehyde (4.48 mL, 41.3 mmol) and few drops of trifluoroacetic acid. The reaction was fitted with Dean- stark apparatus to remove the water. The solution was then heated to reflux for 48 h (55⁰C) while removing the water continuously. After cooling to room temperature, the solvent was evaporated completely. The crude product was then recrystalized from pentane: Ether (5:1) at - 78 ⁰C. The white solid material was filtered thro crucible to give the product 8² (3.23 g, 47.3 % yield). ¹H NMR (500 MHz, CDCl₃) δ 1.00 (s, 9 H), 1.54 (d, J = 7.0 Hz, 3 H), 3.94 (q, J = 6.5 Hz, 1 H), 5.17 (s, 1 H). [α]_D²⁵ -41.6 (c 1.13, CHCl₃).

References:

WO2009/149066,2009,A1 Location in patent:Page/Page column 46