Enzymatic halocyclization of allenic alcohols and carboxylates: A biocatalytic entry to functionalized O-heterocycles

Article abstract of DOI:10.1039/c6gc01926a

Chloroperoxidase from Caldariomyces fumago catalyzes the aerobic oxidative halocyclization of allenic alcohols and carboxylates yielding functionalized furan and pyran heterocycles as valuable synthetic scaffolds. Thanks to an oxidase-initiated redox casc

Full text of DOI:10.1039/c6gc01926a

View Article Online
View Journal
Green
Chemistry
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: J. Naapuri, J. D.
Rolfes, J. Keil, C. Manzuna Sapu and J. Deska, Green Chem., 2016, DOI: 10.1039/C6GC01926A.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/greenchem

Please%do%not%adjust%margins%
Green Chemistry
Page 1 of 7
View Article Online
DOI: 10.1039/C6GC01926A
Green%Chemistry%
%
PAPER%
Enzymatic%Halocyclization%of%Allenic%Alcohols%and%Carboxylates:%
A%Biocatalytic%Entry%to%Functionalized%OCHeterocycles%
Received%00th%January%20xx,%
Accepted%00th%January%20xx%
J.%Naapuri,%J.%D.%Rolfes,%J.%Keil,%C.%Manzuna%Sapu,%and%J.%Deska*%%
DOI:%10.1039/x0xx00000x%
Chloroperoxidase% from% Caldariomyces! fumago% catalyzes% the% aerobic% oxidative% halocyclization% of% allenic%
alcohols% and% carboxylates% yielding% functionalized% furan% and% pyran% heterocycles% as% valuable% synthetic%
scaffolds.%Thanks%to%an%oxidaseAinitiated%redox%cascade,%simple%halide%salts%–%in%combination%with%air%and%
glucose%–%act%as%stoichiometric%reagents%for%the%in%situ%generation%of%reactive%halonium%species.%Under%the%
mild% reaction% conditions% in% an% aqueous% emulsion% medium,% the% stereochemical% integrity% of% diastereoA% and%
enantioenriched%allenes%remains%uncompromised%and%chiral%dihydrofurans%can%be%obtained%via%5AendoAtrig%
cyclizations%with%perfect%axisAtoAcentre%chirality%transfer.%
www.rsc.org/%
!
attracted% much% interest% as% it% enables% the% incorporation% of%
halide% groups% under% very% mild% reaction% conditions.13A16% Here,%
the% substitution% of% high% molecular% weight% organic% halogen%
donors%or%hazardous%dihalogens%by%simple%alkali%halides%and%air%
in% combination% with% the% general% benefits% of% biocatalysis,%
including% high% selectivities,% low% temperatures% and% aqueous%
reaction%media,%can%be%considered%a%major%advancement.%
Introduction%
Halogenation%reactions%play%a%crucial%role%in%organic%synthesis%
as% many% target% structures% in% agricultural% and% pharmaceutical%
chemistry%feature%halide%substitution%patterns.1A3%Furthermore,%
chlorine,%bromine,%and%iodine%atoms%serve%as%highly%important%
functional% groups% in% synthetic% intermediates% allowing% for%
efficient%and%selective%carbonAcarbon%and%carbonAheteroatom%
coupling% reactions.4A6% Classically,% molecular% halogen% has% been%
used%as%reagent%of%choice%for%the%introduction%of%halide%entities%
both% via% radical% pathways% and% as% source% of% electrophilic%
halonium% species.% Due% to% the% harmful,% corrosive% and% toxic%
properties%of%the%lighter%dihalogens,%organic%reagents%such%as%
NAhalosuccinimides,% N,N'Adihalohydantoins,% and% tetrahaloA
methane% have% nowadays% replaced% elemental% X2% to% some%
extent%in%certain%processes.%%
%
Allenes% represent% synthetically% highly% attractive% building%
blocks% that% are% able% to% engage% in% numerous,% partly% unique%
reactions.17A19% Among% these% many% valuable% transformations,%
suitably% decorated% allenes% can% act% as% acceptor% for% halonium%
ions%and%undergo%oxidative%cyclizations%(both%exo8trig20,21%and%
endoAtrig22A25)%that%furnish%heterocyclic%entities%containing%vinyl%
halide%units%as%versatile%functional%handle%for%e.g.%subsequent%
cross% coupling% reactions.% Particularly% gold% catalysis% proved% to%
efficiently%promote%this%kind%of%allene%activation%(Scheme%1,%%
%
In% Nature,% the% major% pathways% for% the% biosynthesis% of%
halogenated% secondary% metabolites% rely% on% the% enzymatic%
oxidative%activation%of%chloride,%bromide,%and%iodide%as%readily%
available%source%of%halogen%atoms.7%Here,%halogenases8,9%and%
haloperoxidases10A12%generate%electrophilic%hypohalide%species%
under% consumption% of% dioxygen% (and% a% suitable% reducing%
agent)%or%hydrogen%peroxide,%respectively.%The%enzymeAbound%
halonium% equivalents% are% subsequently% transferred% to% the%
acceptor% molecules% either% by% direct% proteinAsubstrate%
interaction%or%via%liberation%of%free%hypohalide.%In%recent%years,%
the% synthetic% use% of% halogenating% enzymes% ex! vivo% has%
Krause's gold-catalyzed halogenative cyclization of allenes
O
I
N
I
O
AuCl3 (5 mol%)
CH2Cl2, r.t.
HO
O
1
2
Enzymatic halocyclization based on an aerobic halide oxidation (this work)
R''
R''
X
O2, NaX, D-glucose
R
n
n
haloperoxidase + glucose oxidase
aqueous emulsion
R' HO
R
O
R'
X = Br or I
%
Scheme%1%%%Synthesis%of%halogenated%OAheterocycles%via%oxidative%
halocyclizations.%
This%journal%is%©%The%Royal%Society%of%Chemistry%20xx!
J.!Name.,%2013,%00,%1A3%|%1%%
Please%do%not%adjust%margins%

Please%do%not%adjust%margins%
Green Chemistry
Page 2 of 7
PAPER%
Green%Chemistry%
top),26,27
%
enabling% the% development% of% asymmetric% Table%1%%Enzyme%and%solvent%screening%for%the%bromocyclization%of%3a%a%
View Article Online
DOI: 10.1039/C6GC01926A
halocyclizations.28% Based% on% our% recent% investigations% of% the%
commercial% fungal% chloroperoxidase% from% Caldariomyces!
fumago%(CPO)%as%catalyst%in%oxidative%rearrangement%reactions%
and%the%observation%of%unbeneficial%halide%interferences,29%we%
became%interested%in%the%deliberate%use%of%CPO%as%biological%
mediator% for% the% halogenative% cyclization% of% allenic% alcohols%
and% structurally% related% entities.% Herein,% we% report% on% the%
development% of% a% purely% biocatalytic,% environmentally%
benign,30A32% and% high% yielding% protocol% for% the% synthesis% of%
functionalized% OAheterocycles% based% on% the% halocyclization%
approach%(Scheme%1,%bottom).%In%our%reaction%design,%glucose%
oxidase%(GOx)%served%as%catalyst%for%the%controlled%generation%
of% hydrogen% peroxide% by% reduction% of% aerial% oxygen.%
Subsequent% oxygenation% of% simple% halide% salts% would% render%
reactive% halonium% species% to% trigger% 5A% or% 6AendoAtrigA
cyclizations%with%suitable%allenic%alcohols%or%carboxylates.%
air, NaBr, D-glucose
glucose oxidase
peroxidase
Br
O
additive
aq. buffer
r.t.
OH
3a
4a
%
Entry% Peroxidase%from%
Additive%
%
Conv%
Yield%
%
%
(%)%
(%)!
1%
2%
C.!fumago%
none%
91%
99%
99%
95%
96%
65%
99%
9%
35%
20%
13%
32%
93%
15%
24%
2%
''%
tBuOH%
3%
4%
5%
''%
MeCN%
''%
''%
hexane%
hexane/Brij%35%
MeCN/Brij%35%
hexane/AOT%
hexane/Brij%35%
hexane/Brij%35%
hexane/Brij%35%
hexane/Brij%35%
6%
''%
7%
''%
8%
G.!max%
A.!rusticana!
B.!taurus!
C.!fumago!
Results%&%Discussion%
9%
36%
97%
0%
2%
10%
11%b%
84%
0%
We%commenced%our%studies%with%the%investigation%of%various%
reaction% parameters% that% would% beneficially% influence% the%
5AendoAtrig%bromocyclization%of%model%substrate%3a%employing%
O
O
Brij 35:
AOT:
SO3– Na+
D
Aglucose,%air%and%sodium%bromide%as%stoichiometric%reagents.%
O
O
OH
∼23
An%initial%activity%screening%quickly%revealed%an%optimal%pH%of%
4.5% at% 25% °C,% though,% despite% very% high% conversions% only%
mediocre%yields%of%the%desired%dihydrofuran%4a%were%achieved%
(Table% 1,% entry% 1).% As% already% shown% in% our% previous% CPO%
projects,29%coAsolvents%do%not%only%play%an%important%role%with%
regard% to% substrate% solubility% but% can% be% a% crucial% factor% for%
yield% optimizations% in% peroxidaseAmediated% processes.%
However,%neither%waterAmiscible%coAsolvents%such%as%tBuOH%or%
acetonitrile%(Table%1,%entries%2%&%3)%nor%biphasic%systems%based%
on%hexane%or%toluene%(Table%1,%entry%4)%had%beneficial%effects%
on% the% reaction% outcome.% Interestingly,% the% addition% of%
emulsifiers% –% facilitating% transfer% between% the% phases% –%
influenced% the% biotransformation% in% a% positive% manner% and%
particularly%in%presence%of%the%nonAionic%PEGAbased%detergent%
Brij%35®,32%nearly%full%conversion%and%an%excellent%yield%of%93%%%
was%achieved%(Table%1,%entry%5).%Other%kinds%of%emulsions%or%
microemulsions%utilizing%AOT%as%ionic%surfactant%failed%to%give%
similar% effects% (Table% 1,% entries% 6% &% 7).33% The% optimized%
reaction%medium%consisting%of%aqueous%citrate%buffer,%Brij%35,%
and%hexane%was%also%tested%in%combination%with%other%heme%
enzymes.%While%the%peroxidases%from%soybean%and%horseradish%
delivered% only% trace% amounts% of% the% desired% cyclization%
product% (Table% 1,% entries% 8% &% 9),% halogenation% using% bovine%
lactoperoxidase% proved% to% be% effective% with% almost%
comparably% high% yield% of% 4a% (Table% 1,% entry% 10).% However,%
considering% the% lower% price% of% CPO,% we% chose% the% fungal%
enzyme% as% catalyst% for% more% detailed% studies% on% the%
biocatalytic% allene% cyclization.% The% glucose/glucose% oxidase%
couple%represents%a%very%reliable%and%robust%system%for%the%in!
situ% generation% of% hydrogen% peroxide% via% reduction% of% aerial%
oxygen.%As%a%minor%drawback,%the%overall%atom%efficiency%in%%
O
%
[a]%racA3a%(34.8%mg,%0.2%mmol),%DAglucose%(72%mg,%0.4%mmol),%NaBr%(62%mg,%
0.6%mmol),%additive%(0.2%mmol),%glucose%oxidase%(A.!niger,%50%U),%peroxidase%
(200%U),%citrate%buffer%(0.1%M,%pH%4.5,%10%mL),%hexane%(10%mL),%r.t.,%3A5%h.%
Conversions%and%yields%were%determined%via%1H%NMR%with%dimethylsulfone%
as%standard.%[b]%alternative%H2O2Agenerating%system:%methanol%(1.0%mmol),%
alcohol% oxidase% (P.! pastoris! or% C.! boidinii,% 25% U),% excess% formaldehyde%
dismutase.%
GOxAmediated%reactions%remains%rather%low%since%C6Asugars%as%
sacrificial%reagents%contribute%with%only%two%hydrogen%atoms.%
Here,% shortAchain% primary% alcohols% can% be% considered% an%
elegant,% low% molecular% weight% alternative.34% Unfortunately,%
due% to% the% low% pH% requirement% of% the% CPOAcatalyzed%
halogenation,% all% attempts% to% implement% a% methanol%
oxidase/formaldehyde%dismutase%system35%failed%so%far%(Table%
1,%entry%11).%
%
Although%less%elegant%than%an%enzymatic%system%to%provide%
the%required%low%concentration%of%hydrogen%peroxide,%we%also%
attempted%to%perform%the%oxidative%5AendoAtrig%cyclization%of%
3a% in% a% more% atomAeconomic% manner% in% absence% of% any%
sacrificial%reducing%agents%by%direct%addition%of%aqueous%H2O2.%
Not%surprisingly,%in%presence%of%2%equivalents%of%peroxide,%the%
catalytic% system% was% rapidly% poisoned% and% less% than% 50%%
conversion% was% achieved.% However,% by% periodically% dosing%
small%aliquots%(10%molA%%every%15%min)%of%H2O2,%full%conversion%
could% be% reached% after% 5% hours% and% 4a% was% isolated% in% 80%%
yield%(Scheme%2).%
2%|%J.!Name.,%2012,%00,%1A3%
This%journal%is%©%The%Royal%Society%of%Chemistry%20xx%
Please%do%not%adjust%margins%

Page 3 of 7
Green Chemistry
Please%do%not%adjust%margins%
Green%Chemistry%
%PAPER%
Furthermore,%a%series%of%βAallenols%was%testeVdie%winA%roticrldeeOrn%litnoe%
slow H2O2 addition
%
Br
elucidate%the%potential%use%of%the%oxidasDeO/pI:e1r0o.1x0i3d9a/sCe6%GpCr0o1t9o2c6oAl%
for% the% synthesis% of% halogenated% pyran% building% blocks.% The%
attempt%to%cyclize%the%terminally%dimethylated%but%otherwise%
unsubstituted% alcohol% 5a% failed% and% the% desired% brominated%
pyran%6a%was%observed%only%in%minor%concentrations%(Table%2,%
entry% 1).% Geminal% dimethylation,% either% next% to% the% allene%
function% (5b)% or% at% the% carbinol% carbon% (5c)% led% to% slightly%
improved% yields% of% the% sixAmembered% heterocycles% of% 13%%
(Table% 2,% entry% 2% &% 3).% Although% still% lagging% behind% the% αA
allenol%substrates,%with%the%very%densely%substituted%alcohol%5d%
reasonable% conversions% in% the% halogenative% 6AendoAtrig%
cyclization%were%finally%observed%giving%rise%to%the%bromopyran%
6d%in%46%%yield.%
chloroperoxidase
(C. fumago)
O
citrate buffer (pH 4.5)
NaBr, Brij 35, hexane
r.t.
OH
3a
4a, 80%
%
Scheme%2%%%GlucoseAfree%halogenation%via%periodic%addition%of%H2O2%
%
%
The%optimized%protocol%for%the%enzymatic%halocyclization%of%
allenols% using% the% GOx/CPOAsystem% was% subsequently% tested%
for%its%applicability%on%a%broader%range%of%cumulene%substrates%
(Scheme% 3).% Without% further% adjustments% on% the% catalytic%
method,% full% conversions% were% obtained% for% the% structurally%
related%alcohols%3b%and%3c%giving%rise%to%the%heterocycles%4b%
and%4c%in%high%yields.%To%our%delight,%the%peroxidaseAcatalyzed%
cyclization% also% allowed% for% the% preparation% of% spirocyclic%
brominated% building% blocks% (4d% &% 4e)% and% the% bisA
spirodihydrofuran% 4f.% Furthermore,% the% successful%
halogenation% of% the% allenic% diol% 3g% and% allenol% 3h% with% high%
yields%for%the%bromodihydrofurans%4g%and%4h%proved%that%the%
terminal%disubstitution%pattern%(R%&%R'%≠%H)%is%not%a%necessary%
requirement%for%an%efficient%aerobic%cyclization.%However,%by%
removing%the%gemAdialkyl%or%aryl%substituents,%respectively,%at%
the%allenes'%γAposition%–%that%would%serve%as%stabilizing%factor%
for% potential% cationic% reaction% intermediates% –% substantially%
reduced% yields% were% observed% (4i).% Incubation% of% terminally%
unsubstituted% allenols% did% not% show% any% bromodihydrofuran%
formation% but% instead,% products% arising% from% semipinacol%
rearrangements% were% identified% as% minor% reaction% products%
(<10%%yield).%
Table%2%%%Bromocyclization%of%βAallenols%a%
air, NaBr, D-glucose
glucose oxidase (A. niger)
chloroperoxidase (C. fumago)
R''
R'''
R''
R'''
R'
Br
R
citrate buffer (pH 4.5)
Brij 35, hexane
r.t.
OH
O
R'
R
5a-d
6a-d
%
Entry%
allenol%
R%
R'%
R''%
R'''%
Yield%(%)!
1%
2%
3%
4%
5a%
5b%
5c%
5d!
H%
H%
H%
H%
6a,%4%
Me%
H%
Me%
H%
H%
H%
6b,%13%
6c,%13%
6d,%46%
Me%
Me%
Me%
Me%
H%
Ph%
[a]% 5% (0.2% mmol),% DAglucose% (72% mg,% 0.4% mmol),% NaBr% (62% mg,% 0.6% mmol),%
Brij%35% (0.2% mmol),% glucose% oxidase% (A.! niger,% 50% U),% chloroperoxidase%
(C.!fumago,%200%U),%citrate%buffer%(0.1%M,%pH%4.5,%10%mL),%hexane%(10%mL),%
1
r.t.,% 3A5% h.% Conversions% and% yields% were% determined% via% H% NMR% with%
dimethylsulfone%as%standard.%
air, NaBr, D-glucose
glucose oxidase (A. niger)
chloroperoxidase (C. fumago)
Br
R''
R
R''
R
OH
citrate buffer (pH 4.5)
Brij 35, hexane
r.t.
O
%
As%another%extension%of%this%biocatalytic%allene%activation%
R'
R'
mode,%we%aimed%to%transfer%the%protocol%to%the%cyclization%of%
allenic%carboxylates.%To%our%surprise,%only%traces%of%the%desired%
fiveAmembered% lactones% were% observed% when% 2,3Adienoic%
acids% were% incubated% under% the% previously% optimized%
conditions.% On% the% other% hand,% bromolactonization% of% 3,4A
dienoate%7%resulted%in%the%formation%of%δAlactone%8%as%major%
product% (Scheme% 4).% Considering% the% low% pH% of% the% reaction%
medium% as% a% prerequisite% for% the% CPOAcatalyzed% halide%
oxidation,%the%presence%of%the%lowAnucleophilic%free%acid%might%
attribute%to%the%relatively%sluggish%conversion.%The%use%of%other%
haloperoxidases% with% activity% under% slightly% less% acidic%
conditions%might%therefore%be%beneficial%and%will%be%included%in%
future%studies.%
3a-i
4a-i
Br
Br
Br
O
O
O
4b, 85%
4a, 93%
4c, 81%
Br
Br
Br
O
O
O
4f, 65%
4e, 69%
4d, 74%
Br
Br
Br
OH
air, NaBr, D-glucose
O
O
O
glucose oxidase (A. niger)
chloroperoxidase (C. fumago)
Br
4g, 82 %
4h, 70%
4i, 19%
COOH
citrate buffer (pH 4.5)
Brij 35, hexane
r.t.
O
O
Scheme%3%%%Substrate%scope%of%the%aerobic%bromocyclization%of%αAallenols.%%
This%journal%is%©%The%Royal%Society%of%Chemistry%20xx!
7
8, 34%
%
Scheme%4%%%PeroxidaseAmediated%halolactonization.%
J.!Name.,%2013,%00,%1A3%|%3%
Please%do%not%adjust%margins%

Please%do%not%adjust%margins%
Green Chemistry
Page 4 of 7
PAPER%
In%order%to%investigate%the%stereochemical%integrity%during%
Green%Chemistry%
O
%
View Article Online
DOI: 10.1039/C6GC01926A
1)
2)
lipase (porc. pancreas)
vinyl butyrate
the% oxidative% cyclization% of% diastereoA% or% enantiomerically%
defined% allenic% alcohols,% Thomson's% lanthanumAcatalyzed%
traceless% Petasis% reaction% between% an% alkynyltrifluoroborate%
(9)%and%hydroxycyclohexanone%(10)%was%used%to%synthesize%the%
cyclic% allenol% 11,36% which% was% obtained% in% excellent%
diastereoselectivity% (98%% syn).% Gratifyingly,% the% protocol% for%
the% enzymatic% allenol% cyclization% under% biphasic% conditions%
gave%rise%to%the%desired%bicyclic%dihydrofuran%12%in%89%%yield.%
Most% crucially,% the% relative% synAstereochemistry% was%
quantitatively%transferred%from%the%axially%chiral%allene%moiety%
to% the% newly% formed% centrochiral% heterocycle% with% a%
diastereomeric%excess%of%12%of%98%%(Scheme%5).%
Br
O
Ph
OH
OH
air, NaBr, D-glucose
Ph
O
glucose oxidase (A. niger)
chloroperoxidase (C. fumago)
citrate buffer (pH 4.5)
3g
13, 50%, 98% ee
(over two steps)
Brij 35, hexane, r.t.
via axially chiral allene
O
biocatalytic
desymmetrization
biocatalytic
cyclization
Ph
O
OH
98% ee
%
Scheme%6%%%Multi%enzyme%cascade%for%the%preparation%of%enantiomerically%
pure%3Abromodihydrofurans.%
O
%
%
%
HO
Ph
BF3K
+
%
Finally,%the%application%of%other%halide%salts%was%tested%in%
10
9
order% to% extend% the% protocol% towards% the% chlorination% and%
iodination% of% allenes.% In% presence% of% sodium% chloride,% even%
after%prolonged%reaction%times%only%a%very%low%conversion%was%
observed%(<5%).%In%strong%contrast,%the%corresponding%iodide%
system%provided%a%rapid%and%clean%formation%of%the%iodinated%
cyclization% product% from% 3a% yielding% 14% in% 74%% after% only%
1%hour%(Scheme%7).%Employing%the%diastereomerically%enriched%
alcohol% 11,% also% good% conversion% in% the% iodocyclization% was%
observed.% However,% due% to% partial% epimerization% of% the%
starting% material% under% the% reaction% conditions,% the% bicyclic%
iododihydrofuran% 15% was% obtained% as% mixture% of%
diastereomers.% Further% studies% and% optimizations% regarding%
the% stereochemical% integrity% of% axially% chiral% allenes% in% the%
peroxidaseAmediated%cyclization%are%hence%required%in%order%to%
exploit% this% protocol% also% in% the% synthesis% of% optically% active%
iodinated%OAheterocycles.%
cat. La(OTf)3
2-nitrophenylsulfonyl hydrazide
MeCN
air, NaBr, D-glucose
glucose oxidase (A. niger)
chloroperoxidase (C. fumago)
Br
Ph
12, 89%, 98% syn
Ph
citrate buffer (pH 4.5)
O
OH
H
Brij 35, hexane
r.t.
11, 90%, 98% syn
%
Scheme% 5% % % Perfect% chirality% transfer% in% a% metalAenzymeAcoupled% catalytic%
cascade% for% the% synthesis% of% a% stereochemically% defined% bicyclic% vinyl%
bromide.%
%
Encouraged% by% these% results,% we% turned% our% attention% to%
the%aspect%of%absolute%stereochemistry%and%the%perspective%to%
employ% multiAenzyme% cascades% for% the% preparation% of%
enantioenriched% bromoheterocycles.% On% the% basis% of% a%
previously% described% protocol% for% the% lipaseAmediated%
enantioselective% desymmetrization% of% allenic% diols,37A39% we%
designed%a%twoAstep%sequence%that%allowed%for%the%generation%
of% optically% pure,% axially% chiral% allenols% whose% subsequent%
peroxidaseAcatalyzed% halocyclization% led% to% enantiomerically%
enriched%bromodihydrofurans.%The%stereoselective%acylation%of%
allene%3g%by%lipase%from%porcine%pancreas%with%vinyl%butyrate%
in% 1,4Adioxane% yielded% the% intermediate% allenol% in% excellent%
enantiomeric% excess% of% 98%.% Also% here,% incubation% of% the%
axially%chiral%allene%in%the%oxidase/peroxidase%emulsion%system%
resulted%in%smooth%conversion%to%the%expected%functionalized%
bromide%(S)A13.%Subsequent%basic%hydrolysis%of%the%butyrate%to%
the%alcohol%(S)A4g%and%comparison%of%HPLC%traces%with%those%of%
a%racemic%reference%confirmed%complete%conservation%of%the%
98%% optical% purity% during% the% bromoetherification% (see%
Supplementary%Fig%1).%
I
Ph
Ph
OH
O
air, NaI, D-glucose
glucose oxidase (A. niger)
chloroperoxidase (C. fumago)
3a
14, 74%
or
or
citrate buffer (pH 4.5)
Brij 35, hexane
r.t.
I
Ph
Ph
O
H
OH
11, 98% syn
15, 68%, 70% syn
%
Scheme%7%%%ChloroperoxidaseAtriggered%5AendoAtrig%iodocyclizations.%
Conclusions%
In% this% study,% we% disclosed% that% halideAoxidizing% peroxidases%
can%act%as%highly%efficient%catalysts%for%the%oxidative%5AendoAtrig%
cyclization% of% substituted% αAallenols% yielding% brominated%
dihydrofuran% building% blocks.% Hereby,% the% presented% method%
avoids% any% kind% of% hazardous% elemental% dihalogen% or% high%
molecular%weight%organic%halogen%donors%by%taking%advantage%
%
4%|%J.!Name.,%2012,%00,%1A3%
This%journal%is%©%The%Royal%Society%of%Chemistry%20xx%
Please%do%not%adjust%margins%

Page 5 of 7
Green Chemistry
Please%do%not%adjust%margins%
Green%Chemistry%
%PAPER%
of% an% oxidase/peroxidase% cascade% utilizing% NaBr,% glucose% and% added%to%the%emulsion.%Glucose%oxidase%from%Aspergillus!niger%
View Article Online
aerial% oxygen% as% stoichiometric% reagents% in% an% aqueous% (3% mg,% 50% U,% 0.25% U/µmol)% was% finallDy%OaI:d1d0.e10d3%9t/oC%6sGtCa0rt1%92th6Ae%
emulsion% medium.% In% addition% to% a% wide% substrate% scope% for% reaction.%The%mixture%was%stirred%vigorously%for%3%hours%under%
the% formation% of% fiveAmembered% OAheterocycles,% this% air.% Acetonitrile% (10% mL)% was% added% to% the% mixture% and% the%
biocatalytic%protocol%can%be%employed%to%a%lesser%extend%also% layers%were%separated.%The%aqueous%layer%was%extracted%with%
for%the%synthesis%of%sixAmembered%cyclic%ethers%and%lactones.% nApentane% (3% x% 30% mL).% The% combined% organic% layers% were%
Of%particular%interest%from%a%syntheticAorganic%perspective,%the% washed%with%brine,%dried%over%Na2SO4%and%concentrated%under%
enzymatic% bromocyclization% tolerates% both% stereogenic% reduced%pressure.%Purification%by%flash%chromatography%(SiO2,%
carbinol% centres% and% chiral% allene% axes% and% thus% shows% great% nAhexane/EtOAc,% 9/1)% provided% 4a% (43% mg,% 170% µmol,% 85% %%
potential%for%the%chemoenzymatic%stereoselective%synthesis%of% yield)%as%a%light%yellow%oil.%Rf%(cyclohexane/ethyl%acetate%6/1):%
complex%heterocyclic%target%structure.%%
0.85.%1HCNMR%(400%MHz,%CDCl3):%δ%[ppm]%=%7.39A7.28%(m,%5H),%
5.91%(d,%3J%=%1.6%Hz,%1H),%5.69%(d,%3J%=%1.6%Hz,%1H),%1.50%(s,%3H),%
1.46% (s,% 3H).% 13CCNMR% (100% MHz,% CDCl3):% δ% [ppm]% =% 140.8,%
128.7,%128.3,%126.8,%126.7,%89.1,%85.3,%27.6,%26.2.%FTCIR%(neat,%
ATR):%ν%[cm–1]%=%3064%(w),%3030%(w),%1628%(m),%1454%(s),%1377%
(m),%1361%(m),%1150%(m),%1047%(s),%852%(s),%760%(s),%696%(s).%
Experimental%
General%remarks%
All% reactions% carried% out% under% argon% atmosphere% were%
performed% with% dry% solvents% using% anhydrous% conditions.%
Anhydrous% solvents% were% obtained% from% an% MBraun% MBA
SPS800% drying% system.% Commercially% available% reagents% were%
Acknowledgements%
used%without%further%purification.%Catalysts%and%cofactors%were% We%gratefully%acknowledge%financial%support%provided%by%the%
obtained% from:% NADH,% Carbolution% Chemicals% GmbH;% Suomen% Akatemia% (298250),% the% Deutsche% ForschungsA
Lactoperoxidase%from%Bos!taurus%(LPO),%106%U/mg%(ABTS),%BioA gemeinschaft% (DE1599/4A1)% ERASMUS+% (J.K.),% the% Dr.AOttoA
Research% Products;% Peroxidase% from% Armoracia! rusticana% RöhmAGedächtnisstiftung,%and%Aalto%University.%
(HRP),%148%U/mg%(ABTS),%Sigma;%Peroxidase%from%Glycine!max%
(SBP),% 17.5% kU/mL% (ABTS),% BioAResearch% Products;%
Chloroperoxidase% from% Caldariomyces! fumago% (CPO),% 9.9%
kU/mL%(ABTS),%Sigma;%Glucose%oxidase%type%II%from%Aspergillus!
Notes%and%references%
1
J.%Wang,%M.%SánchezARoselló,%J.%L.%Aceña,%C.%del%Pozo,%A.%E.%
Sorochinsky,% S.% Fustero,% V.% A.% Soloshnok% and% H.% Liu,% Chem.!
Rev.,%2014,%114,%2432.%
L.% N.% HerreraARodriguez,% F.% Khan,% K.% T.% Robins% and% H.AP.%
Meyer,%Chim.!Oggi!Chem.!Today,%2011,%29,%31.%%
L.% N.% HerreraARodriguez,% H.AP.% Meyer,% K.% T.% Robins% and% F.%
Khan,%Chim.!Oggi!Chem.!Today,%2011,%29,%47.%
C.%C.%C.%Johansson%Seechurn,%M.%O.%Kitching,%T.%J.%Colacot%and%
V.%Snieckus,%Angew.!Chem.!Int.!Ed.,%2012,%51,%5062;%Angew.!
Chem.,%2012,%124,%5150%
niger% (GOx),% 17.3% U/mg% (HRP/ABTS),% Sigma;% Alcohol% oxidase%
from% Pichia! pastoris,% 1.1% kU/mL% (HRP/ABTS),% Sigma;% Alcohol%
oxidase% from% Candida! boidinii,% 1.0% U/mg% (HRP/ABTS),% Sigma;%
lipase% from% porcine% pancreas% (PPL),% MP% Biomedicals.% All%
products%were%purified%either%by%column%chromatography%over%
silica% gel% (MachereyANagel% MNAKieselgel% 60,% 40A60% μm,% 240A
400% mesh)% or% by% recrystallization.% Reactions% were% monitored%
by%thin%layer%chromatography%(TLC)%carried%out%on%precoated%
silica%gel%plates%(MachereyANagel,%TLC%Silica%gel%60%F254)%using%
UV% light% and% KMnO4Asolution% or% Hanessian’s% stain% for%
visualization.%1HANMR%and%13CANMR%spectra%were%recorded%at%
room% temperature% on% a% Bruker% Avance% 400% instrument.%
Chemical% shifts% are% reported% in% parts% per% million% (ppm)%
calibrated% using% residual% nonAdeuterated% solvents% as% internal%
reference% (CHCl3%at% 7.26% ppm% (1HANMR)%and%77.16%ppm%(13CA
NMR)).%Infrared%spectra%were%recorded%on%a%Bruker%Alpha%ECOA
ATR% FTAIRASpectrometer,% absorption% bands% are% reported% in%
wave% numbers% [cm–1].% High% performance% liquid% chromatoA
graphy%was%performed%on%a%Waters%system%using%a%Waters%501%
pump%and%a%Waters%2487%dual%detector.%%
2
3
4
5
6
I.% P.% Beletskaya% and% A.% V.% Cheprakov,% Coord.! Chem.! Rev.,%
2004,%248,%2337%
D.%S.%Surry%and%S.%L.%Buchwald,%Angew.!Chem.!Int.!Ed.,%2008,%
47,%6338;%Angew.!Chem.,%2008,%120,%6438.%
7
8
A.%Butler%and%M.%Sandy,%Nature,%2009,%460,%848.%
D.%R.%M.%Smith,%S.%Grüschow%and%R.%J.%M.%Goss,%Curr.!Opin.!
Chem.!Biol.,%2013,%17,%276.%
K.AH.%van%Pée%and%E.%P.%Patallo,%Appl.!Microbiol.!Biotechnol.,%
2006,%70,%631.%
9
10 J.% M.% Winter% and% B.% S.% Moore,% J.! Biol.! Chem.,% 2009,% 284,%
18577.%
11 M.% Hofrichter% and% R.% Ullrich,% Appl.! Microbiol.! Biotechnol.,%
2006,%71,%276.%
12 A.%Butler%and%J.%V.%Walker,%Chem.!Rev.,%1993,%93,%1937.%
13 V.%Weichold,%D.%Milbredt%and%K.AH.%van%Pée,%Angew.!Chem.!
Int.!Ed.,%2016,%55,%6374;%Angew.!Chem.,%128,%6482.%%
14 S.%A.%Shepherd,%C.%Karthikeyan,%J.%Latham,%A.AW.%Struck,%M.%L.%
Thompson,%B.%R.%K.%Menon,%M.%Q.%Styles,%C.%Levy,%D.%Leys%and%
J.%Micklefield,%Chem.!Sci.,%2015,%6,%3454.%%
15 M.% Frese% and% N.% Sewald,% Angew.! Chem.! Int.! Ed.,% 2015,% 54,%
298;%Angew.!Chem.,%2015,%127,%302.%
16 E.%FernándezAFueyo,%M.%van%Wingerden,%R.%Renirie,%R.%Wever,%
Y.%Ni,%D.%Holtmann%and%F.%Hollmann,%ChemCatChem,%2015,%7,%
4035.%
%
Representative%procedure%for%the%enzymatic%halocyclization:%
3CBromoC2,2CdimethylC5CphenylC2,5Cdihydrofuran%(4a).%
nAHexane%(10%mL)%was%added%to%a%solution%of%Brij%35®%(243%mg,%
200%µmol)%in%an%aqueous%citrate%buffer%(10%mL,%0.1%M,%pH%4.5)%
to% form% an% emulsion% by% vigorous% stirring.% Anhydrous% sodium%
bromide%(61%mg,%600%µmol),%DA(+)Aglucose%(72%mg,%400%µmol),%
alcohol% 3a% (200% µmol)% and% chloroperoxidase% from%
Caldariomyces! fumago% (20% µL,% 200% U,% 1% U/µmol)% were% all%
This%journal%is%©%The%Royal%Society%of%Chemistry%20xx!
J.!Name.,%2013,%00,%1A3%|%5%
Please%do%not%adjust%margins%

Please%do%not%adjust%margins%
Green Chemistry
Page 6 of 7
PAPER%
Green%Chemistry%
17 N.%Krause,%A.%S.%K.%Hashmi,%Modern!Allene!Chemistry,%1.%ed.,%
WileyAVCH,%Weinheim,%2004.%
View Article Online
DOI: 10.1039/C6GC01926A
18 S.%Ma,%Acc.!Chem.!Res.,%2003,%36,%701.%
19 S.%Yu%and%S.%Ma,%Chem.!Commun.,%2011,%47,%5384.%
20 M.%Wilking,%C.%G.%Daniliuc%and%U.%Hennecke,%Synlett,%2014,%25,%
1701.%
21 C.%Jonasson,%A.%Horváth%and%J.AE.%Bäckvall,%J.!Am.!Chem.!Soc.,%
2000,%122,%9600.%
22 M.%Hammel%and%J.%Deska,%Synthesis,%2012,%44,%3789.%
23 J.% Deska% and% J.AE.% Bäckvall,% Org.! Biomol.! Chem,.% 2009,% 7,%
3379.%%
24 J.%Li,%C.%Fu,%G.%Chen,%G.%Chai%and%S.%Ma,%Adv.!Synth.!Catal.,%
2008,%350,%1376.%
25 S.%Ma%and%S.%Wu,%Chem.!Commun.,%2001,%441.%
26 B.%Gockel%and%N.%Krause,%Eur.!J.!Org.!Chem.,%2010,%311.%
27 M.% Poonoth% and% N.% Krause,% Adv.! Synth.! Catal.,% 2009,% 351,%
117.%
28 D.%H.%Milles,%M.%Veguillas%and%F.%D.%Toste,%Chem.!Sci.,%2013,%4,%
3427.$%
29 D.% Thiel,% D.% Doknić% and% J.% Deska,% Nat.! Commun.,% 2014,% 5,%
5278.%
30 S.%Wenda,%S.%Illner,%A.%Mell%and%U.%Kragl,%Green!Chem.%2011,%
13,%3007.%
31 R.%A.%Sheldon,%Chem.!Soc.!Rev.,%2012,%41,%1437.%
32 A.%SánchezAFerrer,%R.%Bru%and%F.%GarcíaACarmona,%FEBS,%1988,%
233,%363.%
33 M.%Moniruzzaman,%N.%Kamiya%and%M.%Goto,%Langmuir,%2009,%
25,%977.%
34 S.%Kara,%J.%H.%Schrittwieser,%S.%Gagiulo,%Y.%Ni,%H.%Yanase,%D.%J.%
Opperman,% W.% H.% van% Berkel% and% F.% Hollmann,% Adv.! Synth.!
Catal.,%2015,%357,%1987.%
35 D.%van%der%Waals,%L.%E.%Heim,%S.%Vallazza,%C.%Gedig,%J.%Deska%
and%M.%H.%G.%Prechtl,%Chem.!Eur.!J.,%2016,%22,%11568.%
36 D.%A.%Mundal,%K.%E.%Lutz%and%R.%J.%Thomson,%J.!Am.!Chem.!Soc.,%
2012,%134,%5782.%
37 C.%Manzuna%Sapu,%J.AE.%Bäckvall%and%J.%Deska,%Angew.!Chem.!
Int.!Ed.,%2011,%50,%9731;%Angew.!Chem.,%2011,%123,%9905.%%
38 C.%Manzuna%Sapu%and%J.%Deska,%Org.!Biomol.!Chem.%2013,%11,%
1376.%
39 B.%Skrobo,%J.%D.%Rolfes%and%J.%Deska,%Tetrahedron,%2016,%72,%
1257.%
6%|%J.!Name.,%2012,%00,%1A3%
This%journal%is%©%The%Royal%Society%of%Chemistry%20xx%
Please%do%not%adjust%margins%

Please do not adjust margins
Green Chemistry
Page 7 of 7
View Article Online
DOI: 10.1039/C6GC01926A
Green Chemistry
TOC
Enzymatic Halocyclization of Allenic Alcohols and Carboxylates:
A Biocatalytic Entry to Functionalized O-Heterocycles
Received 00th January 20xx,
Accepted 00th January 20xx
J. Naapuri, J. D. Rolfes, J. Keil, C. Manzuna Sapu, and J. Deska*
DOI: 10.1039/x0xx00000x
www.rsc.org/
Chloroperoxidase (C. fumago) catalyzes the aerobic halogenative 5-endo-trig cyclization of allenes in an
aqueous emulsion system yielding functionalized O-heterocyclic building blocks.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins