Synlett 2010(3): 355-367  
DOI: 10.1055/s-0029-1219154
ACCOUNT
© Georg Thieme Verlag Stuttgart ˙ New York

Enantioenriched Acylated Cyanohydrins: Synthesis and Analysis

Christina Moberg*, Erica Wingstrand
KTH School of Chemical Science and Engineering, Department of Chemistry, SE 100 44 Stockholm, Sweden
Fax: +46(8)7912333; e-Mail: kimo@kth.se;
Further Information

Publication History

Received 7 September 2009
Publication Date:
22 December 2009 (online)

Abstract

The addition of acyl cyanides to prochiral aldehydes catalyzed by a chiral Lewis acid and an achiral Lewis base produces highly enantioenriched O-acylated cyanohydrins. α-Keto esters undergo the same type of addition, although via a different mechanism in which the enantioselectivity originates from a chiral Lewis base. In the presence of a biocatalyst, the minor, undesired enantiomer obtained in the reactions with aldehydes can be selectively hydrolyzed to re-form the starting aldehyde, permitting the reaction to be run in a cyclic manner. The minor-enantiomer recycling results in an essentially enantiopure product. Selective enzymatic hydrolysis is also a key step in high-throughput analysis of conversions and enantiomeric ratios.

1 Introduction

2 Cyanide Sources

3 Enantioselective Acylcyanation of Aldehydes

3.1 Dual Lewis Acid-Lewis Base Activation

3.2 Synthesis of a Herbicide Intermediate

3.3 Mechanistic Aspects

4 Minor-Enantiomer Recycling

5 Enantioselective Addition of Acyl Cyanides to Ketones

5.1 Chiral Lewis Base Catalyzed Addition of Acetyl Cyanide to α-Keto Esters

5.2 Mechanistic Aspects

6 High-Throughput Synthesis and Analysis of O-Acylated Cyanohydrins

6.1 Determination of Enantiomeric Excess

7 Conclusions

12

A few of many examples are listed in refs. 8, 9, 13, and 14, and more examples can be found in the reviews listed in ref. 7.

33

Wingstrand, E.; Moberg, C. unpublished results.

48

Glufosinate was sold by Bayer CropScience for a value of 237 million euros worldwide in 2007; information from (accessed November 10, 2009).

67

In ref. 7f, it is erroneously stated that ‘carefully controlled concentrations and volumes are required for accurate measurements’.