Crystal Structures Of Hydroxynitrile Lyases And Mechanism Of Cyanogenesis

The properties and characteristics of the five HNLs used as catalysts in stereoselective syntheses are listed in Table 2. The crystal structures of these HNLs have been determined during the last decade. From the crystal structures and kinetic measurements, the mechanistic pathways of cyanogenesis could be established.

Table 4

HNL-catalyzed addition of HCN to 4-substituted cyclohexanones

OH CN

cis frans

Aldehyde R =

(S)-MeHNL-catalyzed

(tf)-PaHNL-catalyzed

Aldehyde R =

(S)-MeHNL-catalyzed

(tf)-PaHNL-catalyzed

Time (h)

Conv. (%)

cis:trans

Time (h)

Conv. (%)

cis:trans

Me

2

80

35:65

1.5

99

3:97

Et

5

Quant.

74:36

22

99

2:98

nPr

5

93

96:4

31

83

2:98

iPr

5

Quant.

97:3

22

94

1:99

tBu

3

82

99:1

216

50

10:90

ch2=chch3

9

99

98:2

24

99

1:99

Ph

3

95

99:1

264

71

4:96

Scheme 9: Stereoselective synthesis of cis-p-menthane-1,7,8-triol (A) and cis-p-menth-8-ene-1,7-diol (B).

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