Stereoselectivity of Proline / Cyclobutane Amino Acid-Containing Peptide. Organocatalysts for Asymmetric Aldol Additions: a Rationale

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1 Stereoselectivity of Proline / Cyclobutane Amino Acid-Containing Peptide Organocatalysts for Asymmetric Aldol Additions: a Rationale Ona Illa, *, Oriol Porcar-Tost, Carme Robledillo, Carlos Elvira, Pau Nolis, Oliver Reiser, Vicenç Branchadell, *, Rosa M. Ortuño *, Departament de Química, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain Servei de Ressonància Magnètica Nuclear, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain Institut für Organische Chemie, Universität Regensburg, Universitätsstr. 31, Regensburg, Germany S1

2 TABLE OF CONTENTS - NMR spectra for the structural study of organocatalyst 4 in (CD 3 ) 2 CO, CD 3 CN and CD 3 OD and discussion S3 - NMR spectra for the structural study of organocatalyst 2 and discussion S26 - Circular Dichroism experiments with organocatalyst 4 S33-1 H NMR spectra of organocatalyst 4 using CD 3 OD/D 2 O mixtures S34 - Copies of HPLC chromatograms S35-1 H NMR and 13 C NMR spectra of new compounds S41 - Theoretical calculations S62 - Optimized geometry of 4 in acetone solution - Procedure for the location of transition states - Aldol reaction detailed mechanism between acetone and p-nitrobenzaldehyde catalyzed by 4 - Structures of diastereomeric rate determining transition states for the aldol reaction between acetone and p-nitrobenzaldehyde catalyzed by 3 - Total energy of computed structures - Cartesian coordinates of computed structures - Complete reference 42 S2

3 NMR spectra for the structural study of catalyst 4 in (CD 3 ) 2 CO and (CH 3 ) 2 CO and CD 3 CN 1 H-NMR ((CD 3 ) 2 CO, 600 MHz, 298 K) S3

4 13 C-NMR ((CD 3 ) 2 CO, 600 MHz, 298 K) In blue assignments corresponding to species II and in black to catalyst 4 S4

5 Multiplicity edited HSQC-NMR ((CD 3 ) 2 CO, 600 MHz, 298 K) S5

CD 3 CN, 600 MHz, 298 K containing 15 mg of catalyst 4 and

6 Expansion of the HMBC (CD 3 ) 2 CO, 600 MHz, 298 K) Proposed observed intermediate: Expansion of the HMBC in CD 3 CN, 600 MHz, 298 K containing 15 mg of catalyst 4 and 100 l of non-deuterated acetone Proposed observed intermediate: S6

Relevant NMR assignments for the structural study of catalyst 4 in (CD 3 ) 2 CO Species II (60%) 4 (40%) Difference Numbering 1 H 13 C 1 H 13 C 1 H 13 C 2 4.27 55.46 3.53 46.38 0.70 9.08 5 5.47 67.

7 Relevant NMR assignments for the structural study of catalyst 4 in (CD 3 ) 2 CO Species II (60%) 4 (40%) Difference Numbering 1 H 13 C 1 H 13 C 1 H 13 C Iminium C=N SELECTIVE NOEs for species II ((CD 3 ) 2 CO, 600 MHz, 298 K) S7

8 SELECTIVE NOEs for species II (CD 3 CN, 600 MHz, 298 K) containing 15 mg of catalyst 4 and 100 l of non-deuterated acetone S8

9 NMR spectra for the structural study of catalyst 4 in CD 3 CN 1 H-NMR (CD 3 CN, 600 MHz, 298 K) S9

10 COSY (CD 3 CN, 600 MHz, 298 K) S10

11 13 C{ 1 H}-NMR (CD 3 CN, 150 MHz, 298 K) S11

12 Edited HSQC (CD 3 CN, 600 MHz, 298 K) S12

13 HMBC (CD 3 CN, 600 MHz, 298 K) S13

14 SELECTIVE ROESY (CD 3 CN, 600 MHz, 298 K ) S14

15 NMR spectra for the structural study of catalyst 4 in CD 3 OD 1 H-NMR (CD 3 OD, 600 MHz, 298 K) The * sign refers to the minor conformer signals. S15

16 COSY (CD 3 OD, 600 MHz, 298 K) S16

17 13 C{ 1 H}-NMR (CD 3 OD, 150 MHz, 298 K) S17

18 Edited HSQC (CD 3 OD, 600 MHz, 298 K) Zoom: S18

19 Zoom: S19

20 HMBC (CD 3 OD, 600 MHz, 298 K) S20

21 ROESY (CD 3 OD, 600 MHz, 298 K ) 1 H-NMR (CH 3 OH, 600 MHz, 298 K) S21

22 selective NOESY (CH 3 OH, 600 MHz, 298 K) irradiating the NH7 signal seltocsy (CD 3 OD, 600 MHz, 298 K) S22

23 From the spectra shown above it can be deduced that catalyst 4 presents two major conformations in an 82:18 proportion, as determined by integration of distinctive signals for both conformers in the 1 H-NMR experiment. A 2D ROESY spectrum and a selective NOESY experiment, the latter carried out in non-deuterated methanol, allowed the proposal of two conformations: Figure S1. Equilibrium of the two main conformations of catalyst 4 in methanol solution. In red, observed NOE/ROE contacts from NMR experiments. In blue, bond rotation responsible for two conformations. Numbering of the atoms is arbitrary. The major conformation presents a hydrogen bond between the oxygen atom in CO14 and the hydrogen atom of the carboxylic acid group. This is supported by the existence of ROE contacts between H16 and H10 and between methyl 13 and H16, respectively. The minor conformer does not present the hydrogen bond between CO14 and the acidic proton because the peptide bond between C14 and N15 is rotated so that the carboxylic acid is located far from CO14. This is supported by the existence of a H19*/H10* ROE signal. Both conformers have in common the proximity between NH7 and H11, H5 and H8, respectively, as shown in the selective NOESY experiments S23

24 NMR spectra comparison of catalyst 4 in (CD 3 ) 2 CO, CD 3 CN and CD 3 OD - 1 H-NMR (600 MHz, 298 K) 1 H NMR of catalyst 4 in: a) CD 3 OD; b) CD 3 CN; c) (CD 3 ) 2 CO; d) (CD 3 ) 2 CO after having catalyst 4 stirring in non-deuterated acetone for 1 hour and then evaporating the solvent and performing the NMR, e) CD 3 CN after drying sample d). S24

25 Detail of NMR spectra comparison of catalyst 4 in CD 3 CN and CD 3 OD - 1 H-NMR (600 MHz, 298 K) S25

26 NMR spectra for the structural study of catalyst 2 1 H-NMR (CD 3 OD, 600 MHz, 298 K) S26

27 COSY (CD 3 OD, 600 MHz, 298 K) S27

28 13 C{ 1 H}-NMR (CD 3 OD, 150 MHz, 298 K) Edited HSQC (CD 3 OD, 600 MHz, 298 K) S28

29 HMBC (CD 3 OD, 600 MHz, 298 K) S29

30 ROESY (CD 3 OD, 600 MHz, 298 K) S30

31 selective NOESY (CH 3 OH, 600 MHz, 298 K) irradiating the NH7 signal From the spectra shown above it can be deduced that catalyst 2 presents a single major conformation, which represents more than 90% of the population of conformers. A 2D ROESY spectrum and a selective NOESY experiment, the latter carried out in non-deuterated methanol, allowed the proposal of the following conformation: Figure S2. Major conformation of catalyst 2 in methanol solution. In red, observed NOE/ROE contacts from NMR experiments. In blue, hydrogen bond interactions. Numbering of the atoms is arbitrary. S31

32 The major conformation presents a weak labile hydrogen bond between the oxygen atom in CO12 and the hydrogen atom of the carboxylic acid group. This is supported by the existence of ROE contacts between H14 and H11. CO12 is also involved in a strong hydrogen bond with H7. Selective NOESY experiments show that NH7 is in close proximity with H9, H5 and H4, respectively. S32

33 Circular Dichroism experiments with organocatalyst 4 Compound 4 was dissolved in the desired water/methanol mixture affording a 2.5 mm solution. The CD spectra were recorded on a JASCO-715 spectropolarimeter at 20 ºC. Figure S3. CD spectra of organocatalyst 4 in MeOH (black), MeOH/H 2 O 10:1 (red), MeOH/H 2 O 1:1 (blue), and in H 2 O (green). S33

34 1 H NMR spectra of organocatalyst 4 using CD 3 OD/D 2 O mixtures Figure S4. 1 H NMR (298 K, 400 MHz) spectra of organocatalyst 4 using different deuterated solvents (CD 3 OD and D 2 O). 1: CD 3 OD; 2: CD 3 OD/D 2 O 20:1; 3: CD 3 OD/D 2 O 10:1; 4: CD 3 OD/D 2 O 5:1; 5: CD 3 OD/D 2 O 2:1; 6: CD 3 OD/D 2 O 1:1. S34

35 Copies of HPLC chromatograms Compound 24a, entry 19, Table 1. Compound 24a, entry 38, Table 1. 5 mol% catalyst ent-4, in acetone at 0 o C Hexane/isopropanol 70:30; = 269 nm; 0.5 ml/min t R = 23.3 min (R enantiomer) 93% t R = 32.8 min (S enantiomer) 7% S35

36 Compound 24a, entry 26, Table 1. Compound 24b, entry 10, Table 2. S36

37 Compound 24c, entry 4, Table 2. Compound 24d, entry 5, Table 2. S37

38 Compound 24e, entry 6, Table 2. Compound 24f, entry 7, Table 2. 5 % catalyst 4, in acetone at r.t. Hexane/isopropanol 70/30, = 210 nm, 0.5 ml/min t R = min (S-enantiomer) 85% t R = min (R-enantiomer) 15% S38

39 Compound 24g, entry 8, Table 2. 5 % catalyst 4, in acetone at r.t. Hexane/isopropanol 90/10, = 211 nm, 0.3 ml/min t R = min (S-enantiomer) 85% t R = min (R-enantiomer) 15% Compound 24i, entry 11, Table 2. S39

40 Compound 26, entry 2, Table 3. S40

41 1 H NMR and 13 C NMR spectra of new compounds 1 H-NMR spectrum (250 MHz; CDCl 3 ) 13 C{ 1 H}-NMR spectrum (62.5 MHz; CDCl 3 ) S41

42 1 H-NMR spectrum (250 MHz; CDCl 3 ) 13 C{ 1 H}--NMR spectrum (62.5 MHz; CDCl 3 ) S42

43 1 H-NMR spectrum (600 MHz; CD 3 OD) 13 C{ 1 H}--NMR spectrum (150 MHz; CD 3 OD) S43

44 1 H-NMR spectrum (250 MHz; CDCl 3 ) 13 C{ 1 H}--NMR spectrum (62.5 MHz; CDCl 3 ) S44

45 1 H-NMR spectrum (360 MHz; CDCl 3 ) 13 C{ 1 H}--NMR spectrum (90 MHz; CDCl 3 ) S45

46 1 H-NMR spectrum (400 MHz; CD 3 OD) 13 C{ 1 H}-NMR spectrum (100 MHz; CD 3 OD) S46

47 1 H-NMR spectrum (400 MHz; CD 3 OD) 13 C{ 1 H}-NMR spectrum (100 MHz; CD 3 OD) S47

48 1 H-NMR spectrum (400 MHz; CDCl 3 ) 13 C{ 1 H}-NMR spectrum (100 MHz; CDCl 3 ) S48

49 1 H-NMR spectrum (400 MHz; CD 3 OD) 13 C{ 1 H}-NMR spectrum (100 MHz; CD 3 OD) S49

50 1 H-NMR spectrum (400 MHz; CDCl 3 ) 13 C{ 1 H}-NMR spectrum (100 MHz; CDCl 3 ) S50

51 1 H-NMR spectrum (400 MHz; CD 3 OD) 13 C{ 1 H}-NMR spectrum (100 MHz; CD 3 OD) S51

52 1 H-NMR spectrum (360 MHz; CDCl 3 ) 13 C{ 1 H}-NMR spectrum (90 MHz; CDCl 3 ) S52

53 1 H-NMR spectrum (400 MHz; CDCl 3 ) ent C{ 1 H}-NMR spectrum (100 MHz; CDCl 3 ) ent-15 S53

54 1 H-NMR spectrum (400 MHz; CD 3 OD ) ent-3 S54

55 13 C{ 1 H}-NMR spectrum (100 MHz; CD 3 OD) ent-3 1 H-NMR spectrum (250 MHz; CDCl 3 ) 13 C{ 1 H}-NMR spectrum (62.5 MHz; CDCl 3 ) S55

56 1 H-NMR spectrum (400 MHz; CDCl 3 ) 13 C{ 1 H}-NMR spectrum (100 MHz; CDCl 3 ) S56

57 1 H-NMR spectrum (600 MHz; CD 3 OD) S57

58 13 C{ 1 H}-NMR spectrum (150 MHz; CD 3 OD) 1 H-NMR spectrum (360 MHz; CDCl 3 ) S58

59 13 C{ 1 H}-NMR spectrum (90 MHz; CDCl 3 ) 1 H-NMR spectrum (250 MHz; CDCl 3 ) S59

60 13 C{ 1 H}-NMR spectrum (90 MHz; CDCl 3 ) 1 H-NMR spectrum (360 MHz; CDCl 3 ) S60

61 13 C{ 1 H}-NMR spectrum (90 MHz; CDCl 3 ) 1 H-NMR spectrum (600 MHz; CD 3 OD) CH 2 Cl 2 S61

62 13 C{ 1 H}-NMR spectrum (150 MHz; CD 3 OD) Theoretical Calculations Optimized geometry of 4 in acetone solution Figure S5. Geometry of 4 optimized at the M06-2X/6-31G(d) level of calculation in acetone solution. Selected interatomic distances are in Å. S62

63 Procedure for the location of rate determining transition states. For each transition state a conformational search has been done on a structure such as the one shown in Figure S4 with a C-C distance of 2.0 Å. In all cases two different geometric isomers around the N3=C2 bond have been considered. The most stable structures have been then used as starting points in the direct location of the transition states. Figure S6. Schematic representation of the structures used in the conformational search for the transition states of reactions between an enamine (red) and an aldehyde (blue). Aldol reaction detailed mechanism between acetone and p-nitrobenzaldehyde catalyzed by 4 S63

64 Figure S7. Detailed mechanism proposal for the aldol reaction of acetone and 23a catalyzed by 4. S64

65 Figure S8. Energy (black) and Gibbs energy (blue) profiles for the aldol reaction between acetone and p-nitrobenzaldehyde catalyzed by 4 leading to the formation of (S)-24a. All values in kcal mol -1. Structure of diastereomeric rate determining transition states for the aldol reaction between acetone and p-nitrobenzaldehyde catalyzed by 3 R S Figure S9. Structures of the diastereomeric rate determining transition states corresponding to the aldol reaction between acetone and p-nitrobenzaldehyde catalyzed by 3 in acetone at the M06-2X/6-31G(d) level of calculation. Noncritical hydrogen bonds have been omitted for clarity. Selected interatomic distances are in Å. S65

66 Table S1. Total energies and Gibbs energies in acetone of computed structures (in a.u.) M06-2X/6-31G(d) M06-2X/6-311+G(d,p) E G E a E G Acetone acetone TS(4-I) I TS(I- Ib) Ib TS (Ib-II) II H 2 O TS (II - III) III a S IV S TS (IV-V) S V S VI S TS (VI- VI b) S VI b S TS (VI b- VII) S VII S TS (VII- VIIb) S VIIb S 24a R TS (IV-V) H 2 O R TS(IV-V) H 2 O S TS(IV-V) H 2 O R TS catalyst S TS catalyst a M06-2X/6-311+G(d,p)//M06-2X/6-31G(d) level S66

67 Cartesian coordinates (in Å) of computed structures M06-2X/6-31G(d) geometries 4 C C C C H H N H C O N C C C C H H H H H H H H C O N C C C C H H H H H H H C O O H C H H H C H H H H H Acetone C C H H S67 C H H H H O acetone C C C C H H N H C O N C C C C H H H H H H H C O N C C C C H H H H H H H C O O C H H H C H H H H H C C H

68 H C H H H H H O H TS (4-I) C C C C H H N H C O N C C C C H H H H H H H C O N C C C C H H H H H H H C O O C H H H C H H H H H C C H H C H H H H H O H I C C C C H H N H C O N C C C C H H H H H H H C O N C C C C H H H H H H H C O O C H H H C H H H H H C S68

69 C H H C H H H H H O H TS (I- Ib) C C C C H H N H C O N C C C C H H H H H H H C O N C C C C H H H H H H H C O O C H H H C H H H H H C C H H C H H H H H O H I b C C C C H H N H C O N C C C C H H H H H H H C O N C C C C H H H H H H H C O O C H H H C H H H H S69

70 H C C H H C H H H H H O H TS(I b- II) C C C C H H N H C O N C C C C H H H H H H H C O N C C C C H H H H H H H C O O C H H H C H H H H H C C H H C H H H H H O H II C C C C H H N H C O N C C C C H H H H H H H C O N C C C C H H H H H H H C O O C H H H C H H S70

71 H H H C C H H C H H H H H O H TS (II III) C C C C H H N H C O N C C C C H H H H H H H C O N C C C C H H H H H H H C O O C H H H C H H H H H C C H H C H H H H H O H III C C C C H H N H C O N C C C C H H H H H H H C O N C C C C H H H H H H H C O O C H H H S71

72 C H H H H H C C H H C H H H H H O H a C O H C C C C H C H C H H N O O S IV C C C C H H N H C O N C C C C H H H H H H H C O N C C C C H H H H H H H C O O H C H H H C H H H H H C C H H C H H H C O H C C C C H C H C H H N O O S TS (IV-V) C C C C H H N H C O S72

73 N C C C C H H H H H H H C O N C C C C H H H H H H H C O O H C H H H C H H H H H C C H H C H H H C O H C C C C H C H C H H N O O S V C C C C H H N H C O N C C C C H H H H H H H C O N C C C C H H H H H H H C O O H C H H H C H H H H H C C H H C H H S73

74 H C O H C C C C H C H C H H N O O S VI C C C C H H N H C O N C C C C H H H H H H H C O N C C C C H H H H H H H C O O H C H H H C H H H H H C C H H C H H H C O H C C C C H C H C H H N O O O H H S TS (VI- VI b) C C C C H H N H C O N C C C C H H H H H H H C O N C S74

75 C C C H H H H H H H C O O H C H H H C H H H H H C C H H C H H H C O H C C C C H C H C H H N O O O H H S VI b C C C C H H N H C O N C C C C H H H H H H H C O N C C C C H H H H H H H C O O H C H H H C H H H H H C C H H C H H H C O H C C C C H C H C H H S75

76 N O O O H H S TS( VI b- VII) C C C C H H N H C O N C C C C H H H H H H H C O N C C C C H H H H H H H C O O H C H H H C H H H H H C C H H C H H H C O H C C C C H C H C H H N O O O H H S VII C C C C H H N H C O N C C C C H H H H H H H C O N C C C C H H H H H H H C S76

77 O O H C H H H C H H H H H C C H H C H H H C O H C C C C H C H C H H N O O O H H S TS (VII VII b) C C C C H H N H C O N C C C C H H H H H H H C O N C C C C H H H H H H H C O O H C H H H C H H H H H C C H H C H H H C O H C C C C H C H C H H N O O O H H S VII b C C C S77

SUPPLEMENTARY INFORMATION. Low-molecular-weight gelators consisting of hybrid cyclobutane-based. peptides

SUPPLEMENTARY INFORMATION. Low-molecular-weight gelators consisting of hybrid cyclobutane-based. peptides SUPPLEMENTARY INFORMATION Low-molecular-weight gelators consisting of hybrid cyclobutane-based peptides Sergi Celis, a Pau Nolis, b Ona Illa, a Vicenç Branchadell a and Rosa M. Ortuño* a a Departament