Chemoenzymatic Platform for Synthesis of Chiral Organofluorines Based on Type II Aldolases

Article abstract of DOI:10.1002/anie.201906805

Aldolases are C?C bond forming enzymes that have become prominent tools for sustainable synthesis of complex synthons. However, enzymatic methods of fluorine incorporation into such compounds are lacking due to the rarity of fluorine in nature. Recently, the use of fluoropyruvate as a non-native aldolase substrate has arisen as a solution. Here, we report that the type II HpcH aldolases efficiently catalyze fluoropyruvate addition to diverse aldehydes, with exclusive (3S)-selectivity at fluorine that is rationalized by DFT calculations on a mechanistic model. We also measure the kinetic parameters of aldol addition and demonstrate engineering of the hydroxyl group stereoselectivity. Our aldolase collection is then employed in the chemoenzymatic synthesis of novel fluoroacids and ester derivatives in high stereopurity (d.r. 80–98 %). The compounds made available by this method serve as precursors to fluorinated analogs of sugars, amino acids, and other valuable chiral building blocks.

Full text of DOI:10.1002/anie.201906805

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Accepted Article
Title: Chemoenzymatic platform for synthesis of chiral organofluorines
based on type II aldolases
Authors: Jason Fang, Diptarka Hait, Martin Head-Gordon, and Michelle
Chang
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To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201906805
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10.1002/anie.201906805
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Chemoenzymatic platform for synthesis of chiral organofluorines
based on type II aldolases
Jason Fang[a,b], Diptarka Hait[a,b], Martin Head-Gordon[a,b], and Michelle C. Y. Chang*[a,b,c]
Abstract: Aldolases are C-C bond forming enzymes that have
The aldol addition represents a key reaction in the rapid assembly
become prominent tools for sustainable synthesis of complex
of building blocks with the concomitant generation of two
synthons. However, enzymatic methods of fluorine incorporation into
stereocenters. Controlling the stereoselectivity at both sites is
such compounds are lacking due to the rarity of fluorine in nature.
possible with chiral auxiliaries, precious metal catalysts, or
Recently, the use of fluoropyruvate as a non-native aldolase substrate
organocatalysts.[5] Although numerous and well-developed,
has arisen as a solution. Here, we report that the type II HpcH
these methods still lack in efficiency and universality. The
challenge is magnified for fluorine stereocenters, such that
aldolases efficiently catalyze fluoropyruvate addition to diverse
aldehydes, with exclusive (3S)-selectivity at fluorine that is
asymmetric fluoro-aldol reactions have been reported only
recently.[5c] For these reasons, aldolase enzymes that catalyze the
rationalized by DFT calculations on a mechanistic model. We also
measure the kinetic parameters of aldol addition and demonstrate
addition of a carbonyl donor to an aldehyde acceptor have been
explored as an alternative to chemical methods.[6] Pyruvate
engineering of the hydroxyl group stereoselectivity. Our aldolase
collection is then employed in the chemoenzymatic synthesis of novel
aldolases in particular furnish a useful, densely-functionalized α-
ketoacid motif. However, the donor specificity is usually strict
and fluorine substitution is tolerated in only select cases. In this
fluoroacids and ester derivatives in high stereopurity (d.r. 80-98%).
The compounds made available by this method serve as precursors
to fluorinated analogs of sugars, amino acids, and other valuable
chiral building blocks.
work, we set out to investigate fluoropyruvate aldolases, and to
explore downstream transformations of the resultant ß-fluoro-α-
keto acids into fluorosugars and other important building blocks
for pharmaceuticals.
Fluorine has unique elemental characteristics that have served as
the basis for its rising use in the design of synthetic compounds
There exist four main structural families of pyruvate aldolases,
two belonging to each the type I (KDPG [PF01801] and DHDPS
[PF00701]) and type II (HpcH [PF03328] and DmpG
[PF07836/00782]) mechanistic types. Type I aldolases utilize a
catalytic lysine residue to form a Schiff base with the donor
with
a breadth of functions ranging from materials to
pharmaceuticals.[1] Due to its ability to enhance metabolic
stability and alter pharmacokinetic profiles without adding
significant steric bulk, fluorine is now found in greater than 20%
of drugs.[1a] As such, expanding the scope of accessible
organofluorine structures would greatly enhance our ability to
discover and develop new functional compounds. While many
synthetic methodologies are known for the site-selective
introduction of fluorine onto various scaffolds,[2] fluorine
biocatalysis is less mature yet also offers many potential
advantages with respect to chemo-, regio-, and stereoselectivity
of enzymatic approaches.[3] Our group has focused on biological
synthesis of fluorinated polyketide natural products and
fluorinated polymers,[4] but we also seek to expand biocatalytic
methods for the preparation of broader classes of organofluorine
compounds. One versatile approach to this problem entails the
use of simple fluorinated building blocks in carbon-carbon bond
forming reactions to generate complexity.
[a]
[b]
[c]
J. Fang, D. Hait, Prof. M. Head-Gordon, Prof. M. C. Y. Chang
Department of Chemistry
University of California, Berkeley
Berkeley, CA 94720
J. Fang, D. Hait, Prof. M. Head-Gordon, Prof. M. C. Y. Chang
Chemical Sciences Division
Laurence Berkeley National Laboratory
Berkeley, CA 94720
Prof. M. C. Y. Chang
Department of Molecular & Cell Biology
University of California, Berkeley
Berkeley, CA 94720
E-mail: mcchang@berkeley.edu
Figure 1. Scheme and results of fluoropyruvate addition assay with a panel of
twelve aldehydes. Reactions (50 mM substrates, 0.05 mol% enzyme, 1 mM
MgCl2) were quenched by decarboxylation after 16 h. From left to right in each
group: EcGarL, EcHpcH, SwHpcH1.
Supporting information for this article is given via a link at the end of
the document
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10.1002/anie.201906805
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substrate and have been well-characterized. For example, KDPG
aldolases are powerful biocatalysts with wide acceptor scope for
pyruvate addition, but the ability to utilize fluoropyruvate is
either limited to the native acceptor or non-existent.[7a,b] DHDPS
family aldolases have successfully been used for fluoropyruvate
addition with resulting (3R)-configuration of fluorine, but have
specialized acceptor requirements such as long-chain aldose or
heteroaromatic aldehydes.[7c-e] Furthermore, type I aldolases are
sensitive to high aldehyde concentrations via inhibition of the
catalytic lysine.[8] Thus, we turned our attention to the type II
pyruvate aldolases, which use only a divalent metal cation for
donor binding and enolization.
Figure 2. Mechanistic model of fluoropyruvate aldol addition by HpcH family
pyruvate aldolases for rationalization of the observed stereochemistry. The
(Z)-fluoroenolate geometry, found through DFT calculations to be ~4.6
kcal/mol favored over the (E)-fluoroenolate, gives rise to the (3S)-configuration
of fluorine. The configuration of the hydroxyl group varies depending on the
orientation of the aldehyde.
The type II aldolases have received comparatively little attention
from the biocatalysis community until recently. The DmpG
aldolases typically require complex formation with
dehydrogenases that drive the retro-aldol direction, and thus
appeared less tractable for our synthetic purposes.[9] Therefore,
we initiated investigations into the remaining HpcH aldolase
family, utilizing the five members EcGarL[10], EcRhmA[11], and
EcHpcH[12] from Escherichia coli and SwHpcH1 and SwHpcH2
from Sphingomonas wittichi.[13] Fluoropyruvate addition assays
were conducted by incubation of substrates with enzyme, buffer,
and MgCl2, followed by oxidative decarboxylation with H2O2
and analysis of the α-fluoroacids by 19F NMR (Figure 1). We
initially screened the addition to glycolaldehyde 1e,
dimethoxyacetaldehyde 1f, and glyoxylate 1g in either
phosphate or HEPES buffer, and saw promising overnight
conversions with most enzyme-substrate-buffer combinations
(Figure S2). Using the optimal buffer for each enzyme, the
analysis was then extended to twelve aldehydes 1a-1l
comprising chiral polar, achiral polar, and nonpolar groups. High
to quantitative conversions (80-100%) were achieved for nearly
all combinations of an aldolase with a polar aldehyde (Figure 1).
Nonpolar aldehydes were converted less efficiently (10-70%),
hydroxyacids. From this reaction, only two products were
observed of the four possible diastereomers, with JF-H values
3
indicating a (3S)-configuration of fluorine (Figure S4). Thus the
syn-anti distributions arise from the hydroxyl group, consistent
with reports of HpcH enzymes lacking facial discrimination at
the aldehyde.[11a,12c] Interestingly, these ratios could be dictated
by either the aldehyde or the enzyme in different cases (Figure
1). For example, the ʟ-configured 1b and 1d led to a strong
preference for the anti isomer regardless of enzyme. In contrast,
EcGarL and EcHpcH were strikingly stereocomplementary with
1g (99% syn and 92% anti, respectively). The effect of catalyst
loading on stereochemistry was also investigated in reactions
with 1e and 1f (Figure S2). These aldehydes provided mixtures
of 39-59% anti composition using the standard 0.05 mol%
enzyme, but with 0.01 mol% of enzyme the diastereoselectivity
improved to 71-93% anti at the expense of quantitative
conversions. These data show that careful selection of homologs
and conditions can tune the reaction towards the desired
configuration of the hydroxyl group.
with a preference for propionaldehyde over other alkyl chain We then turned to density functional theory calculations in order
lengths. Steady-state kinetic parameters were measured by a to explore the origin of the stereochemical preference, using the
discontinuous assay with mass spectrometry detection, and were
compared for the EcHpcH-catalyzed addition of either pyruvate the metal-enolate complex (Figure 2). The (3S)-configuration of
proposed mechanism for EcHpcH[12b-d] as a basis for modelling
or fluoropyruvate to glycolaldehyde. We found that the fluorine
fluorine in the aldol adduct is consistent with a bidentate (Z)-
substitution results in a ~500-fold decrease in kcat and the
fluoroenolate intermediate. Density functional theory
appearance of a substrate inhibition phenomenon, but little calculations on a [Mg(H2O)2(OAc)2(Fpyr-enolate)]2- model
change in Km. The kcat defect is largely responsible for the
complex (Figure S5) indicate that the (Z)-isomer is indeed
requirement that fluoropyruvate additions be conducted favored by ~4.6 kcal/mol. The instability of the (E)-isomer likely
overnight, whereas otherwise identical progress assays with
pyruvate reached completion in a few minutes. With this
promising system for fluoropyruvate addition in hand, we sought
to clarify the stereochemical course of the reaction.
partially arises from an unfavorable 1,3-interaction between the
fluorine and carboxylate oxygens, since the free (E)-ligand at
equilibrium features the carboxylate twisted out of plane. Of
note, a (Z)-fluoroenamine has been observed in a type I DHDPS
family aldolase crystal structure,[7c] but this enzyme leads to the
(3R)-configuration of fluorine since the aldehyde binding site is
located on the opposite face of the bound fluoropyruvate. This
supports our working hypothesis that consistent fluorine-
determined electronic features provide a driving force for high
enantioselectivity. However, the absolute configuration of
fluorine that arises depends on which face of the fluoroenolate
or fluoroenamine is exposed to an incoming aldehyde. This is
ultimately dictated by the enzymatic architecture, such that the
fluorine stereocenter may reliably be set as R or S by selecting
an aldolase from the appropriate structural family.
The new fluorine and hydroxyl stereocenters set by
fluoropyruvate addition led us to establish both relative and
absolute stereochemistry by indirect methods. The relative
stereochemistry was preliminarily assigned on the basis of
chemical shift and vicinal coupling constants (3JF-H).[7] For
further confirmation, we synthesized a standard of (2S,3S)-2-
fluoro-3-hydroxysuccinate (anti-4g) and compared it to
enzymatically-derived fluoroacids 4efg using a nitric acid
oxidation strategy (Figure S3). Regarding absolute
configuration, we observed that only one stereogenic center
could be variable, since reactions with chiral aldehydes 1a-1d
gave no more than two peaks in 19F NMR. Also, the aldol adducts
Given our model for the origin of fluorine stereochemistry, we
with achiral aldehydes 3efgj could be reduced enzymatically by next explored how the stereochemistry of the hydroxyl group
lactate dehydrogenase to the corresponding ß-fluoro-α- could be controlled. Although SwHpcH1 and SwHpcH2 were
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Figure 3. EcHpcH variants with phenylalanine point mutations, displaying
complementary and altered stereoselectivity of the hydroxyl group compared to
wild-type. ᴅ-GA: ᴅ-glyceraldehyde 1a; ᴅ-LA: ᴅ-lactaldehyde 1c; GA:
glycolaldehyde 1e; DMA: dimethoxyacetaldehyde 1f.
Figure 4. Compounds produced by chemoenzymatic synthesis. A) Two sets of
three isomers of polyhydroxy α-fluoroacids which were purified by HPLC on a
semi-preparative HILIC column. B) α-Fluoroesters produced from large-scale
biotransformations followed by protection chemistry and isolation by extraction.
anticipated to be stereocomplementary based on a high-
throughput screening study,[13] this was not seen under our
conditions with fluoropyruvate substrate. However, SwHpcH1
was unique in its high anti selectivity with 1f. Sequence
alignment of 459 EcHpcH homologs indicated that variations in
non-catalytic active site residues are fairly common (Figure S7).
In particular, SwHpcH1 features phenylalanine at positions 117
and 210 in place of valine and leucine, respectively, found in the
other four tested homologs. It is possible that the bulkier Phe
residue could modulate the hydroxyl group stereoselectivity by
restricting the poses available to an aldehyde. The V118F,
A174F, and L212F variants of EcHpcH were thus purified for
screening against our aldehyde panel. Notably, EcHpcH A174F
and L212F were stereocomplementary in reactions with ᴅ-
glyceraldehyde 1a and ᴅ-lactaldehyde 1c (Figure 3). Meanwhile,
the V118F variant had high anti selectivity in reactions with 1e
and 1f even at high conversions; the wild-type enzymes achieved
this selectivity only with reduced enzyme loading and sacrificed
conversion. In the course of our study, others showed with
EcRhmA that elimination of bulk in the active site by mutation
of non-conserved residues could broaden the substrate scope.[11e]
Our results show that the opposite strategy of increasing bulk
also has value for improvement or even reversal of
stereoselectivity.
C) Fluorosugars derived from select compounds in groups
characterized by high-resolution MS following oxime derivitization.
A and B;
compounds such as β-fluoro-α-hydroxyacids, β-fluoro amino
acids, and fluorosugars (Figure 5). From the initial ß-fluoro-α-
ketoacid fluoropyruvate adducts, we demonstrate the feasibility
of two enzymatic transformations inspired by the metabolism of
pyruvate in nature: dehydrogenation and transamination. In fact,
commercial lactate dehydrogenase, which we used earlier in
stereochemical experiments, accepted all of 3c-3l as substrates
to afford ß-fluoro-α-hydroxyacids 9c-9l. We further show that
the transaminase from Vibrio fluvialis (VfAT)[14] can convert 3h
and 3j into the corresponding ß-fluoro amino acids 10h and 10j.
Finally, to produce 2′- or 3′-fluorosugars, we subjected the
previously purified acids or esters syn-4a, anti-4a, anti-4b, 6,
and 7 to synthetic routes involving chemical reduction. This
process was successful in producing fluorosugars 11-15, with the
notable pentose fragment 11 being a component of the anticancer
drug Clofarabine which has been targeted for chemoenzymatic
synthesis.[15] These efforts show that these aldolases can serve as
the basis of a platform for stereoselective synthesis of important
motifs that may be difficult to access by other means.
In summary, we have described a type II aldolase family capable
of efficient fluoropyruvate addition to aldehydes with a high
fluorine stereoselectivity. Our quantum mechanical modelling of
the enzyme active site describes the thermodynamic factors that
yield a large driving force for formation of the (Z)-fluoroenolate
and subsequently the (3S)-fluoro product. HpcH aldolases have
recently emerged as suitable engineering targets, and our work
on modulating hydroxyl group stereoselectivity expands this
knowledge base. Taken together, this work offers new
approaches towards the preparation of a range of organofluorine
building blocks, including fluorinated analogs of amino acids,
sugars, and other valuable compounds.
With a collection of wild-type and engineered aldolases in hand,
we desired to demonstrate their applicability by scaling up from
the assay conditions to synthesize fluorinated compounds in high
stereopurity (Figure 4, Table S4). Due to the expensive nature of
chiral aldehydes 1a-d, the corresponding reactions were
conducted on milligram scale with direct purification by
preparative HPLC. This provided the six α-fluoroacids anti-4a-
d
and syn-4ac (d.r. 87-98%), corresponding to three
stereoisomers each of 2-fluoro-3,4,5-trihydroxypentanoate and
2-fluoro-3,4-dihydroxypentanoate. For the inexpensive
aldehydes 1efg we carried out gram scale aldol-esterification
sequences and obtained α-fluoroesters 5-8 (d.r. 80-97%) after
extractive workup. Purified compounds were characterized by
1H, 13C, and 19F NMR and confirmed by high-resolution mass
spectrometry.
Acknowledgments
We thank Dr. Hasan Celik and Dr. Nanette Jarenwattananon (UC
Berkeley College of Chemistry NMR Facility) for NMR
assistance. We also thank Dr. Jonathan McMurry and Dr. Chia-
I Lin (Chang group, former) for materials and valuable advice.
J.F. and M.C.Y.C. were supported by NIH grant 1 R01
The structures accessed by fluoropyruvate addition can serve as
versatile substrates for downstream processing via both
enzymatic and chemical means, thus providing a range of
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Figure 5. Schematic of the pyruvate aldolase platform for organofluorine synthesis. The densely-functionalized fluoropyruvate adducts can be transformed into new
functionalities through decarboxylation, ketoreduction, or transamination. Various fluorosugars can be accessed from fluoroacids by partial reduction of the
carboxylate to an aldehyde (direct strategy) or by full reduction of the carboxylate to an alcohol when R contains a masked aldehyde (inversion strategy). Novel
aldehydes synthesized in this manner could be used as the acceptor in further aldol reactions to incrementally build molecular complexity.
[11]
a) S. Watanabe, M. Saimura, K. Makino, J. Biol. Chem. 2008, 283,
20372–20382. b) D. Rea, R. Hovington, J. F. Rakus, J. A. Gerlt, V.
Fülöp, T. D. H. Bugg, D. I. Roper, Biochemistry 2008, 47, 9955–
9965. c) K. Hernandez, J. Bujons, J. Joglar, S. J. Charnock, P.
Domínguez De María, W. D. Fessner, P. Clapés, ACS Catal. 2017,
7, 1707–1711. d) K. Hernández, A. Gómez, J. Joglar, J. Bujons, T.
Parella, P. Clapés, Adv. Synth. Catal. 2017, 359, 2090–2100. e) K.
Hernández, J. Joglar, J. Bujons, T. Parella, P. Clapés, Angew.
Chem. Int. Ed. 2018, 57, 3583–3587.
GM123181-01. D.H. and M.H.G. were supported by Director,
Office of Science, Office of Basic Energy Sciences, of the U.S.
Department of Energy under Contract No. DE-AC02-
05CH11231.
Keywords: Fluorine, biocatalysis, aldol reaction, lyases
[12]
[13]
a) W. Wang, S. Y. K. Seah, Biochemistry 2005, 44, 9447–9455. b)
D. Rea, V. Fülöp, T. D. H. Bugg, D. I. Roper, J. Mol. Biol. 2007, 373,
866–876. c) W. Wang, P. Baker, S. Y. K. Seah, Biochemistry 2010,
49, 3774–3782. d) M. Coincon, W. Wang, J. Sygusch, S. Y. K.
Seah, J. Biol. Chem. 2012, 287, 36208–36221.
V. De Berardinis, C. Guérard-Hélaine, E. Darii, K. Bastard, V.
Hélaine, A. Mariage, J. L. Petit, N. Poupard, I. Sánchez-Moreno, M.
Stam, et al., Green Chem. 2017, 19, 519–526.
H. S. Bea, S. H. Lee, H. Yun, Biotechnol. Bioprocess Eng. 2011, 16,
291–296.
I. V. Fateev, K. V. Antonov, I. D. Konstantinova, T. I. Muravyova, F.
Seela, R. S. Esipov, A. I. Miroshnikov, I. A. Mikhailopulo, Beilstein J.
Org. Chem. 2014, 10, 1657–1669.
[1]
a) K. Müller, C. Faeh, F. Diederich, Science 2007, 317, 1881–1886.
b) S. Purser, P. R. Moore, S. Swallow, V. Gouverneur, Chem. Soc.
Rev. 2008, 37, 320–330. c) R. Berger, G. Resnati, P. Metrangolo, E.
Weber, J. Hulliger, Chem. Soc. Rev. 2011, 40, 3496–3508.
a) T. Liang, C. N. Neumann, T. Ritter, Angew. Chem. Int. Ed. 2013,
52, 8214–8264. b) X. Yang, T. Wu, R. J. Phipps, F. D. Toste, Chem.
Rev. 2015, 115, 826–870.
a) K. M. Koeller, C. H. Wong, Nature 2001, 409, 232–240. b) B. G.
Davis, V. Boyer, Nat. Prod. Rep. 2001, 18, 618–640. c) M. Hönig, P.
Sondermann, N. J. Turner, E. M. Carreira, Angew. Chem. Int. Ed.
2017, 56, 8942–8973.
a) M. C. Walker, B. W. Thuronyi, L. K. Charkoudian, B. Lowry, C.
Khosla, M. C. Y. Chang, Science 2013, 341, 1089–1094. b) B. W.
Thuronyi, T. M. Privalsky, M. C. Y. Chang, Angew. Chem. Int. Ed.
2017, 56, 13637–13640.
a) B. M. Trost, C. S. Brindle, Chem. Soc. Rev. 2010, 39, 1600–
1632. b) Y. Yamashita, T. Yasukawa, W. J. Yoo, T. Kitanosono, S.
Kobayashi, Chem. Soc. Rev. 2018, 47, 4388–4480. c) J. Saadi, H.
Wennemers, Nat. Chem. 2016, 8, 276–280.
a) S. M. Dean, W. A. Greenberg, C. H. Wong, Adv. Synth. Catal.
2007, 349, 1308–1320. b) M. Brovetto, D. Gamenara, P. Saenz
Méndez, G. A. Seoane, Chem. Rev. 2011, 111, 4346–4403. c) K.
Fesko, M. Gruber-Khadjawi, ChemCatChem 2013, 5, 1248–1272.
a) M. C. Shelton, I. C. Cotterill, S. T. A. Novak, R. M. Poonawala, S.
Sudarshan, E. J. Toone, J. Am. Chem. Soc. 1996, 118, 2117–2125.
b) I. C. Cotterill, D. P. Henderson, M. C. Shelton, E. J. Toone, J.
Mol. Catal. B Enzym. 1998, 5, 103–111. c) J. Stockwell, A. D.
Daniels, C. L. Windle, T. A. Harman, T. Woodhall, T. Lebl, C. H.
Trinh, K. Mulholland, A. R. Pearson, A. Berry, A. Nelson, Org.
Biomol. Chem. 2015, 14, 105–112. d) J. K. Howard, M. Müller, A.
Berry, A. Nelson, Angew. Chem. Int. Ed. 2016, 55, 6767–6770. e)
C. L. Windle, A. Berry, A. Nelson, Curr. Opin. Chem. Biol. 2017, 37,
33–38.
[2]
[3]
[14]
[15]
[4]
[5]
[6]
[7]
[8]
a) H. Nozaki, S. Kuroda, K. Watanabe, K. Yokozeki, Appl. Environ.
Microbiol. 2008, 74, 7596–7599. b) M. Dick, R. Hartmann, O. H.
Weiergräber, C. Bisterfeld, T. Classen, M. Schwarten, P.
Neudecker, D. Willbold, J. Pietruszka, Chem. Sci. 2016, 7, 4492–
4502.
[9]
B. A. Manjasetty, J. Powlowski, A. Vrielink, Proc. Natl. Acad. Sci.
2003, 100, 6992–6997.
[10]
a) B. K. Hubbard, M. Koch, D. R. J. Palmer, P. C. Babbitt, J. A.
Gerlt, Biochemistry 1998, 37, 14369–14375. b) T. Izard, N. C.
Blackwell, EMBO J. 2000, 19, 3849–3856.
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Entry for the Table of Contents
COMMUNICATION
Jason Fang, Diptarka Hait, Martin Head-
Gordon, and Michelle C. Y. Chang*
Page No. – Page No.
Chemoenzymatic
platform
for
synthesis of chiral organofluorines
based on type II aldolases
Biocatalyzed stereoselective organofluorine synthesis: Pyruvate aldolases of
the type II HpcH family are excellent catalysts for fluoropyruvate addition to
aldehydes. The stereoselectivity and kinetic behavior are rationalized, and
engineering of hydroxyl stereoselectivity is demonstrated. Downstream reactions
allow the synthesis of numerous fluorinated analogs of sugars, amino acids, and
other valuable chiral organofluorines.
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