Gram‐Scale Synthesis of Chiral Cyclopropane‐Containing Drugs and Drug Precursors with Engineered Myoglobin Catalysts Featuring Complementary Stereoselectivity

Abstract

Engineered hemoproteins have recently emerged as promising systems for promoting asymmetric cyclopropanations, but variants featuring predictable, complementary stereoselectivity in these reactions have remained elusive. In this study, a rationally driven strategy was implemented and applied to engineer myoglobin variants capable of providing access to 1-carboxy-2-arylcyclopropanes with high trans-(1R,2R) selectivity and catalytic activity. The stereoselectivity of these cyclopropanation biocatalysts complements that of trans-(1S,2S)-selective variants developed here and previously. In combination with whole-cell biotransformations, these stereocomplementary biocatalysts enabled the multigram synthesis of the chiral cyclopropane core of four drugs (Tranylcypromine, Tasimelteon, Ticagrelor, TRPV1 inhibitor 24) in high yield and with excellent diastereo-and enantioselectivity (98-99.9% de; 96-99.9% ee). These biocatalytic strategies outperform currently available methods to produce these drugs. Chiral cyclopropanes à la carteMyoglobin-based cyclopropanation catalysts featuring complementary stereoselectivity for the synthesis of 1-carboxy-2-aryl-cyclopropanes were developed. The engineered hemoproteins were applied in whole-cell reactions to afford cyclopropane-containing drugs and precursors thereof at the gram scale, in high yield and with excellent diastereo-and stereoselectivity.Catalytic methods for the cyclopropanation of olefins cover a prominent role in organic and medicinal chemistry, owing to the recurrence of cyclopropane motifs among biologically active natural products and pharmaceuticals. [1] Significant progress has been made in the development of synthetic methods for asymmetric cyclopropanation, in particular through [+] These authors contributed equally to this work.Supporting information for this article is given via a link at the end of the document. HHS Public Access Author ManuscriptAuthor Manuscript Author ManuscriptAuthor Manuscript the transition metal-catalyzed insertion of carbenoid species into carbon-carbon double bonds. [2] More recently, the Arnold group and our own laboratory have shown that engineered cytochrome P450s [3] and myoglobins (Mb) [4] , respectively, constitute promising catalysts for mediating the cyclopropanation of styrenes in the presence of α-diazoacetate reagents, thus providing a biocatalytic alternative to afford this valuable transformation. Variants of the bacterial cytochrome P450 BM3 were found to favor cis-selectivity in the cyclopropanation of styrene in the presence of ethyl α-diazoacetate (EDA) (P450 BM3 -CIS-T438S: 86% de (cis) , 97% ee (1S,2R) ). [3a] By utilizing a different P450, opposite enantioselectivity was reported by Brustad and coworkers for the cis-cyclopropanation of this substrate, albeit with moderate diastereoselectivity (P450 Biol -T238A: 42% de (cis) , 95% ee (1R,2S) ). [5] Unfortunately, varying cis : trans ratios and degrees of stereoselectivity were exhibited by these enzymes in the presence of other styrene derivatives. [...

β‐Diazocarbonyl Compounds: Synthesis and their Rh(II)‐Catalyzed 1,3 C−H Insertions

“…In contrast to this, no 1,3 CÀHinsertion was observed when using derivative 3n. Both catalysts,R h 2 (OAc) 4 and Rh 2 (TPA) 4 ,e nabled the synthesis of cyclobutene 8 by aw ell-known cyclopropyl carbene ring-expansion of int-6. [27] Then ew stereoselective cyclopropane synthesis represents anew strategy to construct cyclopropane cores from a & b CÀHb onds in aliphatic ketones.…”

“…Since Curtius reported the synthesis of ethyl diazoacetate for the first time in 1883, [1] a-diazocarbonyl compounds have found broad applications in chemical synthesis, [2] chemical biology [3] as well as in the directed evolution of enzymes (Scheme 1a). [4] Thel ong-lasting success of a-diazocarbonyl reagents has been underpinned by the discovery and development of general and efficient synthetic routes for their preparation. [2e, 5] Ak ey feature of a-diazocarbonyl compounds is their ability to generate reactive free carbenes or transition-metalcarbene(carbenoid) species,u pon thermal, photonic or transition-metal catalyst activation.…”

A Continuing Career in Biocatalysis: Frances H. Arnold

“…110 Stereocomplementary biocatalysts are key assets for the synthesis of drugs and complex molecules. 94,[111][112][113][114][115][116][117][118][119] Upon exploring a collection of heme enzymes, the 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Arnold group was able to identify a set of biocatalysts useful for producing the four possible stereoisomers of a cyclopropanation reaction with ethyl diazoacetate and an unactivated alkene (Scheme 2B). 120 Notably, no iron-based catalyst was previously known for this transformation and heme alone only catalyzed this reaction with < 1 turnover.…”

YfeX – A New Platform for Carbene Transferase Development with High Intrinsic Reactivity

“…These biological catalysts lead to a significant reduction in waste and cost in industrial‐scale synthesis compared to stoichiometric syntheses and other catalytic processes [19,20] . In recent years, multiple groups have sought to modify heme proteins (containing Fe porphyrin cofactors) to produce new types of stereoselective and water‐soluble carbene transferases [21–26] . These enzymatic reactions take place under mild conditions and do not require toxic solvents with negative effects on the environment [19,24,27,28] …”