A Biocatalytic Route to Highly Enantioenriched β-Hydroxydioxinones

Article abstract of DOI:10.1002/adsc.201700095

A novel biocatalytic system to access a wide variety of β-hydroxydioxinones from β-ketodioxinones employing commercial engineered ketoreductases has been developed. This practical system provides a remarkably straightforward solution to limitations in acc

Full text of DOI:10.1002/adsc.201700095

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DOI: 10.1002/adsc.201700095
A Biocatalytic Route to Highly Enantioenriched
b-Hydroxydioxinones
Rick C. Betori,a Eric R. Miller,a and Karl A. Scheidta,b,*
a
Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA
E-mail: Scheidt@northwestern.edu
Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208,
b
USA
Received: January 23, 2017; Published online: && &&, 0000
Supporting information for this article can be found under http://dx.doi.org/10.1002/adsc.201700095.
Abstract: A novel biocatalytic system to access
a wide variety of b-hydroxydioxinones from b-keto-
dioxinones employing commercial engineered ke-
toreductases has been developed. This practical
system provides a remarkably straightforward solu-
tion to limitations in accessing certain chemical
scaffolds common in b-hydroxydioxinones that are
of great interest due to their diversification capabil-
ities. A few highlights of this system are that it is
high yielding, highly enantioselective, and chroma-
tography-free. We have demonstrated both a wide
substrate scope and a high degree of scalability.
of a variety of natural products such as exiguolide,[8]
neopeltolide,[9] and okilactomycin,[10] as well as the
total syntheses of many other naturally occurring
compounds.[11]
A conventional approach (Figure 1) to b-hydroxy-
dioxinones (2) involves the Lewis acid-catalysed addi-
tion of dioxinone-derived silyl dienolates (1) to alde-
hydes via a vinylogous Mukaiyama aldol reaction.[12]
A variety of chiral catalysts such as Ti(IV)-BINOL
complexes,[13] Ti(IV)-Schiff base complexes,[14] Si(IV)-
phosphoramidite complexes,[15] and TADDOL cata-
lysts[16] have proven to be competent for this general
transformation.[12b,13–17] Even with the advances in this
Mukaiyama aldol platform, there are still significant
substrate limitations (see below) and the reactions
typically require anhydrous conditions. Notably,
a recent report by Willis using transfer hydrogenation
with a chiral Ru catalyst provides an alternative non-
aldol approach to b-hydroxydioxinone targets.[18]
Keywords: asymmetric synthesis; enzyme catalysis;
hydroxydioxinones; ketoreductases
The synthesis of chiral b-hydroxydioxinones has at- While these approaches have been utilized in total
tracted significant interest because of their use as
building blocks to access functionally diverse prod-
ucts, such as d-hydroxy-b-keto esters and the resulting
syn- and anti-b,d-diol esters.[1] These motifs are com-
monly found in polyketide natural products, which
are known for their potent biological activity and
structural diversity. The complexity of these targets
typically necessitates the construction of these polyol
subunits with high selectivity and efficiency to mirror
what is achieved in nature by polyketide synthetas-
es.[2] d-Hydroxy-b-keto ester scaffolds are also
common in a variety of commercially available statins
and have been shown to be crucial for the observed
biological function of these drugs.[3] Additionally, b-
hydroxydioxinones are also commonly used to access
substituted tetrahydropyranones[4] and d-lactones[5]
and their corresponding dihydropyranones,[6] all of
which are also seen in a variety of biologically active
natural products.[7] These efforts have been of signifi-
Figure 1. Biologically active scaffolds accessed through b-hy-
cant interest to our research group for the synthesis droxydioxinones.
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Whole cell systems for biocatalytic reductions have
been employed, but these processes are traditionally
plagued by low yields and low selectivity. These de-
tracting characteristics are primarily due to the pres-
ence of multiple ketoreductases catalysing the reac-
tion as well as producing undesired impurities.[30] Iso-
lated enzymes are ideal because they can be evaluat-
ed through operationally straightforward, mild reac-
tion conditions with minimal components necessary
for optimization. These attributes make them amena-
ble for rapid reaction development, a component that
is especially attractive in the pharmaceutical industry.
Ketoreductases in nature require NADH or NADPH
as a cofactor for function alongside a dehydrogenase
(formate or glucose) for cofactor regeneration
(Figure 3).[31]
Figure 2. Routes to access chiral b-hydroxydioxinones.
synthesis efforts,[19] these methods are typically limit-
ed by the need for an sp2 center adjacent to the newly
formed stereogenic center for high levels of selectivi-
ty, i.e., unsaturated aldehyde substrates (Figure 2).
Based on our extensive experience with the creation
and use of b-hydroxydioxinones, this pervasive restric-
tion of substrate scope for the established strategies
discussed above has implications in the application of
dioxinone-derived aldol reactions in target synthesis.
For substrates outside of the a,b-unsaturated/aryl
aldehyde limitation, Evans reported the use of benzyl-
ACHTUNGTRENNUNGoxyacetaldehyde with a copper-bisoxazoline catalyst,
but the reaction is restricted to this singular chelating
aldehyde.[17c] Rawal demonstrated that glyoxolate
electrophiles could benefit similarly to the aforemen-
tioned chelation system using TADDOL hydrogen-
bond donors to allow for high selectivity.[16] Notably,
in their recent total synthesis of lyngbouilloside,
Cossy disclosed that using vinylogous Mukaiyama
Figure 3. Catalytic cycle of ketoreductase enzymes.
While these tandem systems have been used exten-
conditions did not provide their desired b-hydroxy- sively,[31] they are potentially problematic when the op-
dioxinone adduct in a stereoselective manner, requir- timal conditions for the ketoreductase and the dehy-
ing them to use preparative supercritical fluid chro- drogenase are not the same. This additional variable
matography to separate the enantiomers.[20] These ex- can necessitate further rounds of enzyme evolution to
amples, combined with previous methods that are obtain an optimal match between the two enzymes.
only practically selective for sp2-type substrates high- Furthermore, due to the use of glucose in these sys-
light situations where there is limited enantio- and tems to turnover glucose dehydrogenase, the resulting
diastereocontrol, force the need for step-uneconomi- gluconolactone is spontaneously hydrolyzed to glu-
cal processes.[21] Taken collectively, these widespread conic acid, requiring additional process controls to
limitations compelled us to investigate a new, comple- maintain the pH of the reaction system in the optimal
mentary approach to the enantioselective construction range. Engineered ketoreductases capable of using
of b-hydroxydioxinones with broad substrate scope isopropyl alcohol (IPA) to regenerate the cofactor
and functional group tolerability.
overcome (i) the tandem optimization issue and (ii)
The use of evolved ketoreductase[22] and p450[23] en- the process parameters for pH control. Typically, the
zymes in synthesis continues to grow rapidly since only additional variable beyond which specific engi-
these complementary catalyst systems (reduction vs. neered ketoreductase to use that needs to be consid-
oxidation, respectively) can produce chiral alcohols ered is its tolerance to organic solvents. This advant-
with high efficiency and superb selectivity.[24] Specifi- age provides unique platforms that grant access to
cally, ketoreductases have been utilized in the produc- substrates that are highly insoluble under aqueous
tion of a variety of statins,[25] b-lactam antibiotics,[26] conditions because of the use of organic solvents. Sur-
anti-inflammatory medicines,[27] cancer treatments[28] prisingly, the application of ketoreductases to the syn-
and other various pharmaceutical building blocks.[29]
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thesis of highly enantioenriched b-hydroxydioxinones
has not been reported to the best of our knowledge.
With this knowledge in hand, we initiated our stud-
ies with b-ketodioxinone 3a by surveying a panel of
isolated enzymes from Codexis Inc. (Table 1) follow-
ing the prescribed screening protocol (see the Sup-
porting Information for details). We selected 3a since
it represented the least biased/most challenging Csp3
substrate with a simple methyl group. In this initial
screen, both KRED-P01-H08 and KRED-P01-C01,
two enzymes that utilized NADPH as the cofactor
Figure 4. Results from conventional routes to b-hydroxy-
dioxinones.
Table 1. Initial enzyme screening results and process target.
and IPA as the reductant, gave b-hydroxydioxinone
4a in >75% yield and >99:1 er (Figure 4). Notably,
all of the enzymes that utilized NADPH as the cofac-
tor provided the (R)-enantiomer (entry 1–19), where
the enzymes that utilized NADH provided the (S)-
enantiomer (entry 20–24). After these initial results,
we sought to improve this process by lowering the
catalyst loading while maintaining greater than 98%
conversion, 98% chemical purity, and 99:1 er
(Figure 4).[32]
Initial attempts to optimize the process using
KRED-P01-H08 were undertaken because it showed
the highest selectivity among the enzymes screened.[27]
However, after considerable effort, the process still
required unreasonably high catalyst loading (10 wt%)
which would not be viable for larger scale reactions
(ꢀ20 g) that were of interest in our laboratory. We
then turned to KRED-P01-C01, and were pleased to
find that b-hydroxydioxinone (4) could be obtained in
68% yield and 99:1 er simply by lowering the catalyst
loading to 5 wt% from the recommended 100 wt%
loading in the screening protocol (Table 2). Evaluat-
ing pH outside of the standard screening conditions
(pH 7) proved to be deleterious to the conversion
(entries 2–6), suggesting that the ketoreductase was
unstable outside of a neutral pH. We next investigat-
ed the use of different co-solvents (@ 10%) with
water/IPA (0.1M phosphate buffer with 10% IPA) to
find that ethereal solvents such as THF, 2-MeTHF,
CPME, MTBE increased yield of this process (en-
tries 7, 11–13). More hydrophobic solvents such as
hexanes and toluene showed slightly decreased yields
(entries 8 and 10). Further investigations with differ-
ent co-solvent percentages showed that organic sol-
vent ratios totaling greater than 20% (e.g., 10% IPA,
10% CPME) reduced the overall yield of product (en-
tries 15–17). The reductions in enzyme catalyst load-
ing to 2 wt% or 1 wt% were not detrimental to the
yield, further demonstrating the robustness of this
process (entries 18 and 19).
[a]
Desired biocatalytic reduction.
Enantioselectivity and conversion of ketoreductases in
Codexis KRED Screening Kit.
Hit criteria in initial screen and final KRED process
[b]
[c]
target.
[d]
Lyophilized cell lysate. Approximately 20–30 wt% of the
lyophilized powder is the catalyst of interest. All referen-
ces to “gLÀ1” used herein will be based on this prepara-
tion.
[e]
On a molar basis, the catalyst loading is on the order of
10À4 to 10À3 mol%.
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Table 2. Optimization of the reaction conditions.[a]
reaction of saturated aldehydes and 1 under Mukaiya-
ma aldol conditions but, as noted above, the typical se-
lectivities for these reactions are <90:10 er. Addition-
ally, sterically encumbered groups adjacent to the
ketone were well tolerated, providing the resulting al-
cohol in excellent yield and enantioselectivity (4o).
Various functional groups such as TMS-protected al-
kynes, Cbz-protected amines, benzyl-protected alco-
hols, alkyl-protected esters and terminal alkenes per-
formed well in this reaction, further highlighting the
tolerance of functional diversity of this methodology
(4p, 4q, 4r, 4t, 4u). Notably, these substrates have not
been accessible in a stereoselective manner using previ-
ous methodologies, allowing for access to more com-
plex scaffolds from these chiral b-hydroxydioxinones.
To further investigate the synthetic utility of this
process, larger scale-up reactions were pursued. Low-
ering the enzyme loading to 0.5 wt% (at a concentra-
tion of 100 gLÀ1) predictably lengthened the overall
reaction time (from 24 h to 72 h) and 20 g of b-hy-
droxydioxinone 4a in 99% yield with >99:1 er were
isolated after a simple extraction (>99% pure as de-
termined by HPLC). Additionally, we wanted to de-
termine if we could access the opposite enantiomer of
b-hydroxydioxinone 4. We were pleased to find that
without optimization, we were able to access b-hy-
droxydioxinone ent-4a in 97% yield with 89:11 er
(Figure 5).
[a]
Conditions: 3a (0.05 mmol), KRED-P01-C01 (0.5 mg),
NADPH (0.1 mg) 1:9 IPA:phosphate buffer (0.1M) at
308C for 24 h.
Determined by HPLC with naphthalene as internal stan-
dard.
Determined by HPLC analysis.
1:1:8 IPA:co-solvent:phosphate buffer (0.1M).
1:0.5:8.5 IPA:co-solvent:phosphate buffer (0.1M).
1:1.5:7.5 IPA:co-solvent:phosphate buffer (0.1M).
1:2:7 IPA:co-solvent:phosphate buffer (0.1M).
1:2.5:6.5 IPA:co-solvent:phosphate buffer (0.1M). THF=
tetrahydrofuran, EtOAc=ethyl acetate, CPME=cyclo-
pentyl methyl ether, MTBE=methyl tert-butyl ether.
[b]
[c]
[d]
[e]
[f]
The resulting b-hydroxydioxinones can be convert-
ed into a variety of motifs relevant to several families
of natural products using previously established chem-
ical routes. Of particular note, dioxinones have exten-
sive precedents in photocycloadditions to access fused
[g]
[h]
For comparison, this optimized biocatalytic reduc-
tion was benchmarked against traditional routes to b-
hydroxydioxinone 4a from b-ketodioxinone 3a includ-
ing chiral hydride sources (i.e., CBS reductions),[33]
transfer hydrogenation and bakerꢁs yeast biocatalysis
(Figure 4). The collected data indicate that this new
ketoreductase protocol provides the desired alcohol
4a in superior yield and selectivity relative to tradi-
tional routes (see the Supporting Information for de-
tails of the experimental conditions).
With these optimized conditions in hand, the scope
for the asymmetric reduction was explored (Table 3).
Overall, the products were obtained in excellent yield
(>90%) and enantioselectivity (>95:5). In all cases,
the products were >95% pure after aqueous work-up,
thereby typically obviating the need for chromatogra-
phy. Aryl substrates that were electron-neutral, as
well as substrates bearing electron-rich and electron-
poor substituents were well tolerated (4b–4m). Sub-
strates with carbon centers adjacent to the newly
formed stereocenter changed from sp2 to sp3 (i.e., “sa-
turated” substrates) provided exquisite selectivity and
Figure 5. Large-scale reduction of b-ketodioxinone and
yield (4n, 4a, 4s). These products correspond to the access to both enantiomers of b-hydroxydioxinone 4a.
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Table 3. Substrate scope.[a]
[a]
See the Supporting Information for details. Yields are of isolated product after extraction. Enantiomeric ratio was deter-
mined by HPLC analysis on a chiral stationary phase.
Absolute configuration was determined by X-ray crystallography of 4b and all other analogues were assigned by analogy.
[b]
cyclic structures common in diterpene natural prod-
In conclusion, we have described herein a biocata-
ucts 5,[34] thermal opening to provide macrocycles of lytic method for the enantioselective reduction of b-
varying sizes 6,[35] and Lewis acid/Bronsted acid-cata- ketodioxinones with sp3 carbons adjacent to the ste-
lysed reactions to form substituted tetrahydropyra- reogenic center, as well as demonstrating access to
nones 7[4,36] (Figure 6).
value-added molecules previously inaccessible in a ste-
reoselective manner. This approach is an attractive,
complementary approach to previously established
aldol-focused methods because of its much broader
substrate scope and operational simplicity. This meth-
odology allows for mild conditions and does not re-
quire the use of high temperature, pressure, or
oxygen-free environments. Investigations in our labo-
ratory towards diastereoselective reductions using ke-
toreductases as well as enzyme immobilization are
currently ongoing.
Experimental Section
General Information
All reactions were carried out under a nitrogen atmosphere
in oven-dried glassware with magnetic stirring. All organic
solvents were purified by passage through a bed of activated
alumina.[37] Reagents were purified prior to use unless other-
Figure 6. Diverse scaffolds accessible with b-hydroxydioxi-
nones.
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wise stated following the guidelines of Chai and Armare-
go.[38] Purification of reaction products was carried out by
flash chromatography using EM Reagent or Silicycle silica
gel 60 (230–400 mesh). Analytical thin layer chromatogra-
phy was performed on EM Reagent 0.25 mm silica gel 60-F
plates. Visualization was accomplished with UV light and
ceric ammonium nitrate stain, potassium permanganate
concentrated under vacuum to obtain the >99% pure b-hy-
droxydioxinone 4a
Procedure for the Preparation of b-
Hydroxydioxinone ent-4a
50 mg of the KRED Recycle Mix N (contains NADH) were
added to a vial. 1 mL of 0.1M phosphate buffer (pH 7.0)
was added to the KRED Recycle Mix N, and stirred until it
was homogeneous, whereupon 1 mg of KRED-NADH 101
was then added. 100 mg of b-ketodioxinone substrate were
then added and the reaction mixture was stirred for 24
hours at 308C. Upon reaction completion, a small amount
of solid NaCl was added to the reaction mixture. The solu-
tion was then filtered, extracted with ethyl acetate (3ꢂ
15 mL), dried with MgSO4, filtered, and then concentrated
under vacuum to obtain the >99% pure b-hydroxydioxi-
none.
1
stain or ninhydrin stain followed by heating. H NMR spec-
tra were recorded on a Bruker Avance 500 MHz w/ direct
cryoprobe (500 MHz) spectrometer and are reported in ppm
using solvent as an internal standard (CDCl3 at 7.26 ppm).
Data are reported as [ap=apparent, s=singlet, d=doublet,
t=triplet, q=quartet, m=multiplet, br=broad; coupling
constant(s) in Hz, integration]. Proton-decoupled 13C NMR
spectra were recorded on a Bruker Avance 500 MHz w/
direct cryoprobe (125 MHz) spectrometer and are reported
in ppm using solvent as an internal standard (CDCl3 at
77.16 ppm). Mass spectra data were obtained on a Waters
Acquity-H UPLC-MS with a single quadrupole ESI Spec-
trometer or on a Gas Chromatography Mass Spectrometer
(Agilent 7890A/5975C GCMS System).
CCDC 1516986 contains the supplementary crystallo-
graphic data for this paper. These data can be obtained free
of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
Acknowledgements
Research reported in this publication was supported by
NIGMS/NIH under Award Number T32GM105538. The au-
thors would like to thank Louis Redfern and Charlotte Stern
(Northwestern) for assistance with crystallography studies
General Procedure for the Preparation of b-Hydroxy-
dioxinones 4a–4u
50 mg of the KRED Recycle Mix P (contains NADPH)
were added to a vial. 0.8 mL of 0.1M phosphate buffer
(pH 7.0) were added to the KRED Recycle Mix P, and
stirred until it was homogeneous, whereupon 1 mg of
KRED-P01-C01 was then added. In a separate vial, 100 mg
of b-ketodioxinone substrate, 0.1 mL isopropyl alcohol
(IPA) and 0.1 mL cyclopentylmethyl ether (CPME) were
added. Once the b-ketodioxinone substrate had completely
dissolved, this solution was added to the solution containing
KRED-P01-C01. The reaction mixture was stirred for 24
hours at 308C. Upon reaction completion, a small amount
of solid NaCl was added to the reaction mixture. The solu-
tion was then filtered, extracted with ethyl acetate (3ꢂ
15 mL), dried with MgSO4, filtered, and then concentrated
under vacuum to obtain the >99% pure b-hydroxydioxi-
none.
References
[1] J. Krꢃger, E. M. Carreira, Tetrahedron Lett. 1998, 39,
7013.
[2] J. Staunton, K. J. Weissman, Nat. Prod. Reports 2001,
18, 380.
[3] a) Y. Wu, F.-J. Xiong, F.-E. Chen, Tetrahedron 2015, 71,
8487; b) E. F. Oliveira, D. Santos-Martins, A. M. Ri-
beiro, N. F. Brꢄs, N. S. Cerqueira, S. F. Sousa, M. J.
Ramos, P. A. Fernandes, Expert Opinion on Therapeu-
tic Patents 2016, 1.
[4] W. J. Morris, D. W. Custar, K. A. Scheidt, Org. Lett.
2005, 7, 1113.
[5] a) J. Gleitz, J. Friese, A. Beile, A. Ameri, T. Peters,
Eur. J. Pharmacol. 1996, 315, 89; b) P. P. Reddy, K.-F.
Yen, B.-J. Uang, J. Org. Chem. 2002, 67, 1034; c) G. E.
Stokker, W. F. Hoffman, A. W. Alberts, E. J. Cragoe,
A. A. Deana, J. L. Gilfillan, J. W. Huff, F. C. Novello,
J. D. Prugh, J. Med. Chem. 1985, 28, 347.
[6] a) A. Goel, V. J. Ram, Tetrahedron 2009, 65, 7865;
b) M. D. Aytemir, ꢅ. C¸ alis¸, M. ꢆzalp, Arch. Pharm.
2004, 337, 281.
Procedure for the Large-Scale Preparation of 4a
160 mL of 0.1M phosphate buffer (pH 7.0) were added to
a 500-mL, 3-neck, round-bottom flask equipped with an
overhead stirrer, a nitrogen inlet, and a septum. 100 mg of
KRED-P01-C01 were then added followed by 50 mg of
NADPH. In a separate 100-mL round-bottom flask, 20 g of
b-ketodioxinone substrate 3a, 20 mL isopropyl alcohol
(IPA) and 20 mL cyclopentyl methyl ether (CPME) were
added. Once the b-ketodioxinone substrate had completely
dissolved (required slight heating and stirring), this solution
was added to the solution containing KRED-P01-C01. The
reaction mixture was stirred for 72 hours at 308C. Upon re-
action completion, solid NaCl was added to the reaction
mixture. The solution was then filtered, extracted with ethyl
acetate (5ꢂ150 mL), dried with MgSO4, filtered, and then
[7] W. Li, X.-B. Li, L. Li, R.-J. Li, H.-X. Lou, Phytochemis-
try Lett. 2015, 12, 22.
[8] E. A. Crane, T. P. Zabawa, R. L. Farmer, K. A. Scheidt,
Angew. Chem. 2011, 123, 9278; Angew. Chem. Int. Ed.
2011, 50, 9112.
[9] a) D. W. Custar, T. P. Zabawa, K. A. Scheidt, J. Am.
Chem. Soc. 2008, 130, 804; b) D. W. Custar, T. P.
Zabawa, J. Hines, C. M. Crews, K. A. Scheidt, J. Am.
Chem. Soc. 2009, 131, 12406.
Adv. Synth. Catal. 0000, 000, 0 – 0
6
ꢀ 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÞÞ
These are not the final page numbers!

COMMUNICATIONS
asc.wiley-vch.de
[10] J. M. Tenenbaum, W. J. Morris, D. W. Custar, K. A.
Scheidt, Angew. Chem. 2011, 123, 6014; Angew. Chem.
Int. Ed. 2011, 50, 5892.
2016, 3162; b) S. K. Ma, J. Gruber, C. Davis, L.
Newman, D. Gray, A. Wang, J. Grate, G. W. Huisman,
R. A. Sheldon, Green Chem. 2010, 12, 81.
[11] a) K. C. Nicolaou, R. Guduru, Y. P. Sun, B. Banerji,
D. Y. K. Chen, Angew. Chem. 2007, 119, 6000; Angew.
Chem. Int. Ed. 2007, 46, 5896; b) S. B. J. Kan, K. K. H.
Ng, I. Paterson, Angew. Chem. 2013, 125, 9267; Angew.
Chem. Int. Ed. 2013, 52, 9097; c) R. Cookson, T. N. Bar-
rett, A. G. M. Barrett, Acc. Chem. Res. 2015, 48, 628.
[12] a) G. Casiraghi, L. Battistini, C. Curti, G. Rassu, F. Za-
nardi, Chem. Rev. 2011, 111, 3076; b) G. Casiraghi, F.
Zanardi, G. Appendino, G. Rassu, Chem. Rev. 2000,
100, 1929.
[26] J. Liang, E. Mundorff, R. Voladri, S. Jenne, L. Gilson,
A. Conway, A. Krebber, J. Wong, G. Huisman, S.
Truesdell, J. Lalonde, Org. Process Res. Dev. 2010, 14,
188.
[27] J. Liang, J. Lalonde, B. Borup, V. Mitchell, E. Mun-
dorff, N. Trinh, D. A. Kochrekar, R. Nair Cherat, G. G.
Pai, Org. Process Res. Dev. 2010, 14, 193.
[28] X. Ju, Y. Tang, X. Liang, M. Hou, Z. Wan, J. Tao, Org.
Process Res. Dev. 2014, 18, 827.
[29] a) R. N. Patel, ACS Catal. 2011, 1, 1056; b) U. T. Born-
scheuer, G. W. Huisman, R. J. Kazlauskas, S. Lutz, J. C.
Moore, K. Robins, Nature 2012, 485, 185; c) J. T.
Kuethe, J. M. Janey, M. Truppo, J. Arredondo, T. Li, K.
Yong, S. He, Tetrahedron 2014, 70, 4563.
[13] M. De Rosa, M. R. Acocella, R. Villano, A. Soriente,
A. Scettri, Tetrahedron: Asymmetry 2003, 14, 2499.
[14] R. A. Singer, E. M. Carreira, J. Am. Chem. Soc. 1995,
117, 12360.
[15] S. E. Denmark, T. Wynn, G. L. Beutner, J. Am. Chem.
Soc. 2002, 124, 13405.
[16] V. B. Gondi, M. Gravel, V. H. Rawal, Org. Lett. 2005,
7, 5657.
[30] D. J. Pollard, K. Telari, J. Lane, G. Humphrey, C.
McWilliams, S. Nidositko, P. Salmon, J. Moore, Biotech-
nol. Bioeng. 2006, 93, 674.
[31] T. Matsuda, R. Yamanaka, K. Nakamura, Tetrahedron:
[17] a) J. Krꢃger, E. M. Carreira, J. Am. Chem. Soc. 1998,
120, 837; b) S. E. Denmark, J. R. Heemstra, G. L. Beut-
ner, Angew. Chem. 2005, 117, 4760; Angew. Chem. Int.
Ed. 2005, 44, 4682; c) D. A. Evans, M. C. Kozlowski,
J. A. Murry, C. S. Burgey, K. R. Campos, B. T. Connell,
R. J. Staples, J. Am. Chem. Soc. 1999, 121, 669.
[18] Z. Fang, G. J. Clarkson, M. Wills, Tetrahedron Lett.
2013, 54, 6834.
[19] a) Y. Kim, R. A. Singer, E. M. Carreira, Angew. Chem.
1998, 110, 1321; Angew. Chem. Int. Ed. Engl. 1998, 37,
1261; b) D. A. Evans, E. Hu, J. D. Burch, G. Jaeschke,
J. Am. Chem. Soc. 2002, 124, 5654; c) I. Paterson,
R. D. M. Davies, R. Marquez, Angew. Chem. 2001, 113,
623; Angew. Chem. Int. Ed. 2001, 40, 603; d) S. E. Den-
mark, S. Fujimori, J. Am. Chem. Soc. 2005, 127, 8971;
e) S. M. Dalby, J. Goodwin-Tindall, I. Paterson, Angew.
Chem. 2013, 125, 6645; Angew. Chem. Int. Ed. 2013, 52,
6517.
[20] A. Kolleth, J. Gebauer, A. ElMarrouni, R. Lebeuf, C.
Prꢇvost, E. Brohan, S. Arseniyadis, J. Cossy, Frontiers
in Chemistry 2016, 4.
[21] a) B. B. Snider, F. Song, Org. Lett. 2001, 3, 1817; b) R.
Munakata, H. Katakai, T. Ueki, J. Kurosaka, K.-i.
Takao, K.-i. Tadano, J. Am. Chem. Soc. 2003, 125,
14722.
[22] a) G. W. Huisman, J. Liang, A. Krebber, Curr. Opin.
Chem. Biol. 2010, 14, 122; b) A. M. Bezborodov, N. A.
Zagustina, Applied Biochemistry and Microbiology
2016, 52, 237.
[23] a) R. Fasan, ACS Catal. 2012, 2, 647; b) H. Renata,
Z. J. Wang, F. H. Arnold, Angew. Chem. 2015, 127,
3408; Angew. Chem. Int. Ed. 2015, 54, 3351.
Asymmetry 2009, 20, 513.
[32] D. J. Pollard, J. M. Woodley, Trends Biotechnol. 2007,
25, 66.
[33] E. J. Corey, C. J. Helal, Angew. Chem. 1998, #110, 2092;
Angew. Chem. Int. Ed. Engl. 1998, 37, 1986.
[34] a) J. D. Winkler, K. E. Henegar, P. G. Williard, J. Am.
Chem. Soc. 1987, 109, 2850; b) J. D. Winkler, C. L.
Muller, J. P. Hey, R. J. Ogilvie, N. Haddad, P. J. Squat-
trito, P. G. Williard, Tetrahedron Lett. 1989, 30, 5211;
c) J. D. Winkler, B. Shao, Tetrahedron Lett. 1993, 34,
3355; d) J. D. Winkler, E. M. Doherty, Tetrahedron
Lett. 1998, 39, 2253; e) J. D. Winkler, E. C. McLaughlin,
Org. Lett. 2005, 7, 227.
[35] a) R. K. Boeckman, J. R. Pruitt, J. Am. Chem. Soc.
1989, 111, 8286; b) R. K. Boeckman Jr, T. E. Barta,
S. G. Nelson, Tetrahedron Lett. 1991, 32, 4091; c) R. K.
Boeckman, P. Shao, S. T. Wrobleski, D. J. Boehmler,
G. R. Heintzelman, A. J. Barbosa, J. Am. Chem. Soc.
2006, 128, 10572; d) K. P. Reber, S. D. Tilley, E. J. Sor-
ensen, Chem. Soc. Rev. 2009, 38, 3022; e) S. D. Tilley,
K. P. Reber, E. J. Sorensen, Org. Lett. 2009, 11, 701;
f) T. R. Hoye, M. E. Danielson, A. E. May, H. Zhao,
Angew. Chem. 2008, 120, 9889; Angew. Chem. Int. Ed.
2008, 47, 9743; g) T. R. Hoye, M. E. Danielson, A. E.
May, H. Zhao, J. Org. Chem. 2010, 75, 7052; h) Y. M.
Zhao, T. J. Maimone, Angew. Chem. 2015, 127, 1239;
Angew. Chem. Int. Ed. 2015, 54, 1223.
[36] a) J. Wang, E. A. Crane, K. A. Scheidt, Org. Lett. 2011,
13, 3086; b) J. Cui, D. I. Chai, C. Miller, J. Hao, C.
Thomas, J. Wang, K. A. Scheidt, S. A. Kozmin, J. Org.
Chem. 2012, 77, 7435.
[37] A. B. Pangborn, M. A. Giardello, R. H. Grubbs, R. K.
Rosen, F. J. Timmers, Organometallics 1996, 15, 1518.
[38] W. L. F. Armarego, C. L. L. Chai, in: Purification of
Laboratory Chemicals, 6th edn., (Eds.: W. L. F. Armare-
go, C. L. L. Chai), Butterworth-Heinemann, Oxford,
2009, p 88.
[24] H. Grçger, W. Hummel, S. Borchert, M. Kraußer, in:
Enzyme Catalysis in Organic Synthesis, Wiley-VCH,
Weinheim, 2012, p 1035.
[25] a) S. Tartaggia, S. Fogal, R. Motterle, C. Ferrari, M.
Pontini, R. Aureli, O. D. Lucchi, Eur. J. Org. Chem.
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