Reaktion #51488

Reaktionsgleichung

cysteine ethyl ester hydrochloride

triethylamine

dibromoethane

4-Boc-thiomorpholine-3-carboxylic acid

→

thiomorpholinecarboxylic acid ethyl ester

Ausbeute 87.0%

Lösungsmittel

THF

Reaktionsbedingungen

Aufarbeitung

1. 1
   Sonstigecan be prepared in the following manner
2. 2
   Temperaturrefluxing for 16 hours
3. 3
   Sonstigethe solids were removed by filtration
4. 4
   SonstigeThe solvent was removed in vacuo
5. 5
   Sonstigethe residue was chromatographed on silica

Vorschrift

4-Boc-thiomorpholine-3-carboxylic acid can also be substituted for the compound of formula (XXIV) in Reaction Scheme 7 and can be prepared in the following manner: To THF was added cysteine ethyl ester hydrochloride (1.15 g, 6.18 mmol), triethylamine (4.17 mL, 30 mmol) and dibromoethane (2.51 mL, 6.2 mmol). After stirring for 1 hour and refluxing for 16 hours, the solids were removed by filtration. The solvent was removed in vacuo and the residue was chromatographed on silica to give thiomorpholinecarboxylic acid ethyl ester (0.94 g, 87%). The ester (15.3 g, 95 mmol) was dissolved in dioxane/water (1/1) and di-t-butyldicarbonate (24 g, 110 mmol) and LiOH were added. After stirring for 3 hours, the solvent was removed in vacuo and the pH was adjusted to 3 with KHSO3 and extracted with ethyl acetate. The organic layer was separated, washed with brine, dried (MgSO4), and the solvent was removed in vacuo to give 17.4 g (78%) 4-Boc-thiomorpholine-3-carboxylic acid: 1H NMR (CDCl3) δ 1.45 (m, 9), 2.45 (m, 1), 2.71 (m, 1). 2.93 (m, 1), 3.10 (m. 1), 3.29 (m, 1), 4.11 (m, 1), 4.19 (m, 1), 5.20 (m, 1).

Quelle