Page 99 - Chiral Separation Techniques

3.7 Combinatorial Libraries of Selectors for HPLC 75

Enantioselectivity

(R) trp (S) trp (S) t-leu (R) tyr (S) tyr (R) phe (S) his (S) ser (S) asn (S) gln

aa 2 (S) phe (R) i-leu (S) i-leu (R) leu (S) leu (R) val (S) val (S) glu (S) asp (S) arg aa 1

Fig. 3-7. Evaluation of a focused library of 71 DNB-dipeptide CSPs for enantioseparation of the test
racemate 8. (Reprinted with permission from ref. [86]. Copyright 1999, American Chemical Society.)

Fig. 3-8. HPLC evaluation of a 250 × 4.6 mm i.d.
analytical column packed with the selected dipep-
tidic (S)-Glu-(S)-Leu-DNB CSP. Conditions:
mobile phase 20 % 2-propanol in hexane, flowrate
–1
2.0 mL min , UV detection at 280 nm. (Reprinted
with permission from ref. [86]. Copyright 1999,
American Chemical Society.)

Fig. 3-9. Preparative HPLC of 100 mg of the test racemate 8 in a single 2 mL injection using a 250 ×
4.6 mm i.d. column containing (S)-Glu-(S)-Leu-DNB CSP. Conditions: mobile phase ethyl acetate,
–1
–1
flowrate 2.0 mL min , UV detection at 380 nm. Injection 2 mL of 50 mg mL racemate solution. Frac-
tions collected before and after the indicated cut point were 98.4 % ee and 97 % ee pure, respectively.
(Reprinted with permission from ref. [86]. Copyright 1999, American Chemical Society.)