تفاعل #64781

معادلة التفاعل

bis(trimethylsilyl)trifluoroacetamide

ethyl acetate

2-trifluoromethyl-3-acetylthiopropionyl chloride

bis(trimethylsilyl)trifluoroacetamide

L-leucine

→

N-[2-[(Acetylthio)methyl]-3,3,3-trifluoro-1-oxopropyl]-L-leucine

المذيبات

methanol

acetic acid

hexane

acetonitrile

acetonitrile

ظروف التفاعل

المعالجة

1. 1
   درجة الحرارةwas cooled to 0°-5° C.
2. 2
   أخرىresulted in a clear lemon color solution
3. 3
   workup.STIRRINGon additional stirring for one hour at room temperature
4. 4
   درجة الحرارةThe reaction mixture was cooled to 0°-5° C.
5. 5
   workup.ADDITIONwas added dropwise over 45 minutes
6. 6
   workup.STIRRINGAfter stirring for 1.5 hours at 0°-5° C. to room temperature
7. 7
   أخرىcompletion of the reaction
8. 8
   أخرىThe reaction mixture was evaporated under reduced pressure
9. 9
   أخرىto give a yellow oily residue which
10. 10
    أخرىwas partitioned between ethyl acetate (75 mL) and water (50 mL)
11. 11
    استخلاصThe aqueous phase was further extracted with ethyl acetate (4×50 mL)
12. 12
    غسيلthe combined extracts were washed with 75 mL of brine
13. 13
    تجفيفdried (MgSO4)
14. 14
    أخرىevaporated
15. 15
    أخرىto give 10.3 g
16. 16
    أخرىchromatographed on 75 g
17. 17
    أخرىof silica gel eluting with ethyl acetate: hexanes:acetic acid, 100:100:1 to yield 0.15 g
18. 18
    غسيلof the faster eluting diastereomer (isomer A) and 0.12 g
19. 19
    غسيلof slower eluting diastereomer (isomer B)
20. 20
    أخرىchromatographed similarly (silica gel, 1300 g.) which
21. 21
    أخرىgave 2.5 g
22. 22
    workup.ADDITIONof a mixture of both the diastereomers, and 1.5 g
23. 23
    أخرىThe mixed fractions were rechromatographed
24. 24
    أخرىto give 0.5 g
25. 25
    أخرىtriturated with hexanes containing a few drops of ethyl acetate
26. 26
    ترشيحfiltered
27. 27
    أخرىdried
28. 28
    أخرىto yield 2.57 g

الإجراء التجريبي

A stirred suspension of L-leucine (2.62 g., 20 mmol) in 35 mL of dry acetonitrile under argon was cooled to 0°-5° C. and bis(trimethylsilyl)trifluoroacetamide (10.62 mL, 40 mmol) was added. The reaction mixture was allowed to stir while slowly warming to room temperature. After 2 hours, another 3.5 mL (13 mmol) of bis(trimethylsilyl)trifluoroacetamide was added which resulted in a clear lemon color solution on additional stirring for one hour at room temperature. The reaction mixture was cooled to 0°-5° C. and 2-trifluoromethyl-3-acetylthiopropionyl chloride (4.69 g., 20 mmol.) dissolved in 8 mL of acetonitrile was added dropwise over 45 minutes. After stirring for 1.5 hours at 0°-5° C. to room temperature, TLC shows completion of the reaction. The reaction mixture was evaporated under reduced pressure to give a yellow oily residue which was partitioned between ethyl acetate (75 mL) and water (50 mL). The aqueous phase was further extracted with ethyl acetate (4×50 mL), the combined extracts were washed with 75 mL of brine, dried (MgSO4), and evaporated to give 10.3 g. of a yellow semi-solid residue. A 0.68 g. portion of this crude material was flash chromatographed on 75 g. of silica gel eluting with ethyl acetate: hexanes:acetic acid, 100:100:1 to yield 0.15 g. of the faster eluting diastereomer (isomer A) and 0.12 g. of slower eluting diastereomer (isomer B). The remaining 9.6 g. of crude material was flash chromatographed similarly (silica gel, 1300 g.) which gave 2.5 g. of isomer A, 2.7 g. of a mixture of both the diastereomers, and 1.5 g. of isomer B. The mixed fractions were rechromatographed using the same conditions to give 0.5 g. of isomer A and 1.25 g. of isomer B. Both the 2.5 g. and 0.5 g. portions of isomer A were combined, triturated with hexanes containing a few drops of ethyl acetate, filtered, and dried to yield 2.57 g. of the title isomer A product as a white crystalline solid, m.p. 150°-152° C., TLC Rf =0.40 (100:50:1 ethyl acetate:hexane:acetic acid), [α]D =-146.9° (c=1.00, methanol).

المصدر