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. Author manuscript; available in PMC: 2020 Jan 4.
Published in final edited form as: ACS Catal. 2018 Nov 20;9(1):242–252. doi: 10.1021/acscatal.8b04132

Table 1.

Initial Peptide sequence optimization.a,b

graphic file with name nihms-1007693-t0012.jpg
entry Catalyst
 conv (%)c erd
PG i i + 1 i + 2 i + 3
1 P3 Fmoc pThr(Bn) d-Pro Acpc Leu-NMe2 87 64:36
2 P4 Fmoc pThr(Bn) d-Pro Acpc Leu-d-Phe-NMe2 67 66:34
3 P5 Fmoc pThr(Bn) d-Pro Acpc Phe-NMe2 88 64:36
4 P6 Fmoc pThr(Bn) d-Pro Acpc Ala-NMe2 85 62:38
5 P7 Fmoc pThr(Bn) d-Pro Aib Phe-NMe2 92 69:31
6 P8 Fmoc pThr(Bn) d-Pro Aib d-Phe-NMe2 69 52:48
7 P9 Fmoc pThr(Bn) Pro Aib Phe-NMe2 54 44:56
8e P8 Fmoc pThr(Bn) d-Pro Aib Phe-NMe2 19 51:49
9 P10 Fmoc Thr(Bn) d-Pro Aib Phe-NMe2 <5 n/a
10 P11 Fmoc pThr(H) d-Pro Aib Phe-NMe2 44 55:45
11 P12 Fmoc allo-pThr(Bn) d-Pro Aib Phe-NMe2 47 51:49
12 P13 Fmoc pPhSer(Bn) d-Pro Aib Phe-NMe2 98 67:33
13 P14 Fmoc pSer(Bn) d-Pro Aib Phe-NMe2 73 58:42
14 P15 Fmoc-Phe pThr(Bn) d-Pro Aib Phe-NMe2 96 70:30
15 P16 Fmoc-d-Phe pThr(Bn) d-Pro Aib Phe-NMe2 88 67:33
16 P17 Fmoc-Pro pThr(Bn) d-Pro Aib Phe-NMe2 88 72:28
17 P18 Fmoc-d-Pro pThr(Bn) d-Pro Aib Phe-NMe2 93 73:27
18f P18 Fmoc-d-Pro pThr(Bn) d-Pro Aib Phe-NMe2 73 (75)g 78:22
19h P18 Fmoc-d-Pro pThr(Bn) d-Pro Aib Phe-NMe2 50 77:23
20h (R)-1b 97 64:36
a

Reaction conditions: Cyclobutanone 4b (0.05 mmol, 1.0 equiv) at 0 → 4 °C (ambient temperature) with [4b] = 0.10 M CHCl3.

b

Reported results are the average of two trials.

c

Determined by 1H NMR relative integrations.

d

Enantiomeric ratios were determined by CSP-HPLC analysis (Chiralpak IA, 210 nm). Absolute configuration was not determined.

e

Reaction performed with f-BuOOH (70% w/w aq. 1.5 equiv).

f

Reaction was carried out at −15 °C.

g

Yield in parentheses determined by 1H NMR internal standard (1,3,5-trimethoxybenzene).

h

Reaction was carried out at −25 °C.

Abbreviations: pThr, phosphothreonine; Bn, benzyl; Acpc, 1-aminocyclopropane carboxylic acid; Aib, 2-aminoisobutryic acid; pPhSer, β-threo-phosphophenylserine; pSer, phosphoserine, Bz, benzoyl.