Synthesis of deuterated mevalonolactone isotopomers

Article abstract of DOI:10.1002/ejoc.201100188

A synthetic route was developed for the preparation of deuterated mevalonolactones. Using low-cost deuterated reagents, this route allows for the independent introduction of deuterium labeling into any carbon position or into any combination of positions. Following this approach, the synthesis of [6,6,6-²H₃]mevalonolactone, [4,4,6,6,6-²H ₅]mevalonolact-one, [5,5-²H₂]mevalonolactone, [5,5,6,6,6-²H₅]mevalonolact-one, and [2,2,6,6,6- ²H₅]mevalonolactone is described.

Full text of DOI:10.1002/ejoc.201100188

FULL PAPER
DOI: 10.1002/ejoc.201100188
Synthesis of Deuterated Mevalonolactone Isotopomers
Jeroen S. Dickschat,*[a] Christian A. Citron,[a] Nelson L. Brock,[a] Ramona Riclea,[a] and
Henning Kuhz[a]
Keywords: Synthetic methods / Natural products / Isotopic labeling / Biosynthesis / Terpenoids / Mevalonate pathway
A synthetic route was developed for the preparation of deu-
terated mevalonolactones. Using low-cost deuterated rea-
gents, this route allows for the independent introduction of
bination of positions. Following this approach, the synthesis
of [6,6,6-2H3]mevalonolactone, [4,4,6,6,6-2H5]mevalonolact-
one, [5,5-2H2]mevalonolactone, [5,5,6,6,6-2H5]mevalonolact-
deuterium labeling into any carbon position or into any com- one, and [2,2,6,6,6-2H5]mevalonolactone is described.
safety standards required for the manipulation of radioac-
Introduction
tive material are drawbacks. Feeding experiments with 13C-
Modern methods for investigating biosynthetic pathways
to natural products include genetic and enzymologic experi-
ments, such as gene knockouts, expressions of genes or
whole biosynthetic gene clusters in heterologous hosts, and
incubations of purified enzymes with their natural sub-
strates or analogs. Using isotopically labeled precursors,
classical feeding experiments can give additional infor-
mation and are in general easily carried out, as they are
only limited by the availability of labeled compounds. The
incorporation of the isotopic label into the natural product
can be followed by the analysis of crude extracts, through
a combination of chromatographic methods and mass spec-
trometry (mainly HPLC–MS or GC–MS) or by NMR spec-
troscopy completed after the purification of the natural
product.[1] These facile approaches make feeding experi-
ments a very powerful tool for the elucidation of biosyn-
thetic pathways. A wide range of isotopically labeled com-
pounds, including amino acids, sugars, C2 and C3 building
blocks such as acetate and pyruvate, and other primary me-
tabolites, are available from commercial suppliers. However,
if more specialized questions are addressed, unusual precur-
sors or precursors with an isotopic label in specific posi-
tions may be required, and therefore, synthesis may be nec-
essary. These syntheses can be highly complex and labori-
ous, and the isotopically labeled starting materials or rea-
gents are usually expensive. Therefore, short, efficient, and
flexible routes are required.
labeled compounds can give insight into the origin of the
carbon backbone of a natural product, and rearrangements
of the carbon skeleton may also be followed. One of the
most prominent examples is the discovery and elucidation
of the deoxyxylulose phosphate pathway to plant and bac-
terial terpenoids, such as the ginkgolides from Gingko bi-
loba and hopanoids from Rhodopseudomonas palustris.[2] In
these studies, a labeling pattern in the terpenes was found
which could not be explained by the well-known mevalon-
ate pathway. In addition, a rearrangement in an early step
of the newly discovered deoxyxylulose phosphate pathway
was demonstrated. A major advantage of 13C labeling is the
convenient detection of its incorporation using 13C NMR
spectroscopy. As the natural abundance of 13C is only about
1%, very low incorporation rates already result in a signifi-
cant increase of the corresponding NMR signal. However,
if the 13C labeling occurs in different neighboring carbons
and with high incorporation rates, highly complex 13C
NMR spectra may be obtained due to the 13C-13C cou-
plings. Therefore, dilution experiments are sometimes per-
formed to limit the percentage of recovered label in the nat-
ural product.[3]
The incorporation of deuterium can also be followed
1
using NMR spectroscopy. As the natural abundance of H
is nearly 100%, higher incorporation rates are required for
1
significant effects in the H NMR spectrum. Deuterium la-
beling is particularly useful for investigating volatile natural
products using GC–MS, because deuterated compounds
have shorter retention times than their unlabeled analogs,
and the incorporation of one deuterium usually results in a
decrease of the retention index by one unit.[4] The shortened
retention times are caused by an isotopic effect which re-
sults in a significantly shorter C–D bond compared to a C–
H bond. This effect is not significant in the case of other
isotopic pairs, such as a 13C–H bond compared to a 12C–H
bond. As a consequence of the bond shortening, the polar-
3
Besides radioactive isotopes such as 14C and H, most
biosynthetic studies make use of 13C or 2H. Radioactive
labels can be detected with very high sensitivity using radio-
graphic methods. However, the health hazards and the high
[a] Institut für Organische Chemie, Technische Universität
Braunschweig,
Hagenring 30, 38106 Braunschweig, Germany
Fax: +49-531-3915272
E-mail: j.dickschat@tu-bs.de
Eur. J. Org. Chem. 2011, 3339–3346
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3339

J. S. Dickschat, C. A. Citron, N. L. Brock, R. Riclea, H. Kuhz
FULL PAPER
izability of a deuterated compound is lower than that for starting material. Monoprotection of 3a by treatment with
its unlabeled counterpart. Therefore, the van der Waals in- NaH and benzyl bromide gave 4a that was then oxidized
teractions between the deuterated material and the station- using pyridinium chlorochromate (PCC) to the correspond-
ary phase of the GC are weaker, and this results in shorter ing aldehyde 5a. The first deuterium label was introduced
retention times of the deuterated analyte. As a consequence, by a Grignard reaction using [2H3]methylmagnesium iodide,
the mass spectra of the pure deuterated compounds are not prepared from [2H3]methyl iodide, and resulted in alcohol
superimposed by those of the unlabeled compounds.
6a. Oxidation of 6a with PCC afforded ketone 7a which
For investigations of the biosynthesis of terpenoids, deu- then underwent H/D exchange (hydrogen/deuterium ex-
terated pathway intermediates are frequently required. The change) with potassium carbonate in deuterium oxide to
biosynthesis of terpenes proceeds from linear precursors, give 7b. Subsequent addition of ethyl bromoacetate in a Re-
such as geranyl diphosphate (GPP, to monoterpenes), far- formatsky reaction with Rieke zinc yielded ester 8b. Re-
nesyl diphosphate (FPP, to sesquiterpenes), or geranylger- moval of the benzyl protecting group by a catalytic hydro-
anyl diphosphate (GGPP, to diterpenes), via cationic inter- genation reaction resulted in the free alcohol without any
mediates that are generated by abstraction of the diphos- detectable loss of the deuterium label according to 1H
phate moiety or by protonation of an isoprenoid double NMR spectroscopy or GC–MS analysis. The product
bond.[5] The structurally complex polycyclic carbon back- underwent a spontaneous partial cyclization which went to
bone of a terpene is formed by cyclization steps in which completion upon further treatment with p-TsOH to form
olefinic double bonds attack cationic centers, and Wagner– [4,4,6,6,6-2H5]MVA (1b).
Meerwein shifts and hydride migrations may occur. Ter-
mination mechanisms include deprotonating a late cationic
intermediate or having it undergo a nucleophilic attack by
water, for example. The hydride shifts and deprotonation
steps can only be followed by using deuterated pathway in-
termediates, and few synthetic routes to deuterated isotopo-
mers of mevalonolactone[6] or deoxyxylulose[7] have been
published. Synthetic routes to isotopically labeled mevalon-
olactones and their applications in biosynthetic investi-
gations have also been reviewed.[8] In a previous publication
we reported the synthesis of [4,4,6,6,6-2H5]mevalonolactone
(MVA), which was used to investigate the biosynthesis of
geosmin to prove a critical hydride migration,[9] and of 2-
methylisoborneol.[10] Both are frequently occurring volatiles
produced by several streptomycetes and myxobacteria.
Using the same synthetic strategy as that for [4,4,6,6,6-2H5]-
MVA, the synthesis of further MVA isotopomers is re-
ported herein.
Results and Discussion
The aim of our work was to develop a synthetic route to
deuterated mevalonolactones that allows for the indepen-
dent introduction of deuterium into any position or into
any combination of different positions using low-cost deu-
terated reagents. Following this approach, compounds
[6,6,6-2H3]MVA (1a), [4,4,6,6,6-2H5]MVA (1b), [5,5-2H2]-
MVA (1c), [5,5,6,6,6-2H5]MVA (1d), and [2,2,6,6,6-2H5]-
MVA (1e) were synthesized (Figure 1).
Figure 1. Synthesized deuterated mevalonolactones 1a–e.
The original synthesis[9] of [4,4,6,6,6-2H5]MVA (1b) was
carried out using propane-1,3-diol (3a, Scheme 1) as the Scheme 1. Synthesis of deuterated mevalonolactones 1a–e.
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Eur. J. Org. Chem. 2011, 3339–3346

Synthesis of Deuterated Mevalonolactone Isotopomers
The same sequence of steps was carried out for the syn- lonate with D2O as in the synthesis of 1b, by the reduction
thesis of [6,6,6-2H3]MVA (1a). In this case, the step intro- of diethyl malonate with LiAlD4 as in the syntheses of 1c
ducing deuterium to 7a to give 7b was omitted, and 7a was and 1d, by the Grignard reaction using [2H3]methylmagne-
directly converted by the addition of ethyl bromoacetate sium iodide as in the syntheses of 1a, 1b, 1d, and 1e, or by
into ester 8a. For our generalized approach, this introduc- the nucleophilic addition of [2H3]acetonitrile, instead of
tion of deuterium by H/D exchange with deuterium oxide ethyl bromoacetate, to ketone 7c as in the synthesis of 1e.
was problematic, because the independent deuteration of All these deuterated reagents are comparably cheap, and
either the methyl group or the methylene group next to the the introduction of deuterium at any carbon in mevalonol-
carbonyl function was not possible. A second problem with actone is possible. 1H NMR spectroscopy and GC–MS
this reaction was described in a previous[9] publication, that analysis verified that all the deuterated isotopomers of mev-
is, the use of a relatively strong base such as sodium meth- alonolactone were obtained with a high percentage of deu-
oxide in MeOD for the H/D exchange resulted in the elimi- terium content, usually more than 99% in the target posi-
nation of benzyl alcohol from 7a, whereas the use of a mild tions. No deuterium was accidentally introduced at other
base such as K2CO3 in deuterium oxide required a pro- carbons by potential side reactions. However, during the
longed reaction time of seven days for the completion of synthesis of aldehyde 5b by oxidation with PCC, a slight
the H/D exchange. To circumvent these problems, we devel- loss of Ͻ5% of deuterium content was observed as a conse-
oped a new synthetic route to [4,4,6,6,6-2H5]MVA (1b) quence of the C,H-acidity at the α-position. Fortunately,
starting from diethyl malonate (2a). The H/D exchange this loss will not be critical for the application of the meva-
using potassium carbonate in deuterium oxide proceeded lonolactone isotopomers derived from 5b in biosynthetic in-
smoothly and gave 2b with a deuterium content of Ͼ99% vestigations.
in the central methylene group. Lithium aluminium hydride
reduction of 2b gave 3b, monobenzylation of the diol gave
Conclusions
4b, and oxidation of the alcohol with PCC produced 5b
with a slight deuterium loss (Ͻ5%) caused by the acidity
of the α-position. The Grignard reaction with [2H3]methyl-
magnesium iodide gave alcohol 6b, and subsequent oxi-
dation yielded ketone 7b that was further processed to 1b
through the established route. Using the unlabeled Grig-
nard reagent, methylmagnesium iodide, would allow for the
synthesis of [4,4-2H2]MVA and, therefore, the independent
introduction of deuterium into the 4- or 6-positions of mev-
alonolactone is possible with this route.
The known synthesis of [4,4,6,6,6-2H5]MVA (1b)[9] was
improved and modified, resulting in a highly flexible route
to deuterated mevalonolactones that may be independently
labeled in any carbon position or in any combination of
positions. The applicability of this route was demonstrated
in the synthesis of four additional isotopomers of mevalono-
lactone, [6,6,6-2H3]MVA (1a), [5,5-2H2]MVA (1c),
[5,5,6,6,6-2H5]MVA (1d), and [2,2,6,6,6-2H5]MVA (1e). To-
gether with 1b, these compounds are useful for investigating
the biosynthesis of terpenoids. Our approach also makes
new mevalonolactones available, as synthetic routes towards
1d and 1e were previously unpublished. Application of
these labeled mevalonolactones to biosynthetic investi-
gations will soon be carried out in our laboratory.
The synthesis of [5,5-2H2]MVA (1c) was carried out from
2a by a reduction with lithium aluminium deuteride to give
3c. The following steps included protection of 3c to give
benzyl ether 4c, oxidation of the alcohol with PCC to give
5c, and Grignard reaction of 5c with methylmagnesium io-
dide to give 6c. Oxidation of the alcohol to ketone 7c was
followed by the nucleophilic addition with ethyl bromoacet-
ate to give 8c. Removal of the benzyl protecting group fol-
lowed by cyclization afforded 1c. A drawback of this route
was the loss of 50% of the deuterium label during the oxi-
dation reactions to 5c and 7c. Similarly, [5,5,6,6,6-2H5]MVA
(1d) was prepared from 5c by treatment with [2H3]methyl-
magnesium iodide to yield 6d that proceeded to the target
compound through 7d and 8d.
Experimental Section
General Synthetic Methods: Chemicals were purchased from Acros
Organics (Geel, Belgium) or Sigma Aldrich Chemie GmbH (Stein-
heim, Germany) and used without further purification. Solvents
were purified by distillation and dried according to standard meth-
ods. For all general procedures, the relative amounts of the reagents
are given as equivalents (equiv.) referring to the molar ratios of the
compounds, and the relative amounts of the solvents are given as
Instead of the addition of ethyl bromoacetate through a
Reformatsky reaction, the alternative nucleophilic addition the final concentrations of the transformed starting material (set
of [2H3]acetonitrile to aldehyde 7a was applied to the syn-
to 1.0 equiv.). Thin-layer chromatography was performed with the
0.2 mm precoated plastic sheets Polygram® Sil G/UV254 (Machery-
thesis of [2,2,6,6,6-2H5]MVA (1e). The respective reaction
Nagel). Column chromatography was carried out using Merck sil-
gave compound 8e that was deprotected by catalytic hydro-
ica gel 60 (70–200 mesh). 1H NMR and 13C NMR spectra were
genation. Saponification of the nitrile was carried out with
recorded with a Bruker AMX400 spectrometer, UV spectra were
NaOD in deuterium oxide to prevent a deuterium washout
obtained with a Varian Cary 100 Bio, and IR spectra were recorded
in the methylene group adjacent to the nitrile function. This
directly resulted in the formation of 1e.
with a Bruker Tensor 27 ATR (attenuated total reflectance). GC–
MS analyses were carried out with an Agilent 7890A connected to
an Agilent 5975C inert mass detector fitted with a BPX-5 fused
The major advantage of our synthetic method is the pos-
sibility of labeling any position of mevalonolactone. This
silica capillary column (25 m, 0.25 mm i. d., 0.25 μm film). Instru-
can be accomplished by the H/D exchange of diethyl ma- mental parameters were (1) inlet pressure, 77.1 kPa, He
3341
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J. S. Dickschat, C. A. Citron, N. L. Brock, R. Riclea, H. Kuhz
FULL PAPER
23.3 mLmin–1, (2) injection volume, 2 μL, (3) transfer line, 300 °C,
and (4) electron energy, 70 eV. The GC was programmed as follows:
5 min at 50 °C increasing at 5 °Cmin–1 to 320 °C, and operated in
split mode (20:1, 60 s valve time). The carrier gas was He at
1 mLmin–1. Retention indices (I) were determined from a homolo-
gous series of n-alkanes (C8–C38).
diethyl ether, and the organic layer was dried with MgSO4 and
concentrated in vacuo. The residue was purified by column
chromatography on silica gel (hexane/ethyl acetate, 1:1) to give
monoprotected alcohols 4a–c as colorless oils. For 4b and 4c, a
deuterium content of Ͼ99% determined by 1H NMR spectroscopy
and GC–MS analysis was found. For all three compounds the cor-
responding dibenzyl ethers were also formed in minor amounts
(17–28%).
[2,2-2H2]Diethyl Malonate (2b): To a solution of diethyl malonate
(16.0 g, 100 mmol) in D2O (200 mL) was added anhydrous K2CO3
(1.36 g, 10 mmol, 0.10 equiv.). The reaction mixture was stirred for
24 h at room temperature and afterwards extracted with diethyl
ether (3ϫ). The combined organic layers were dried with MgSO4,
and the solvent was removed under reduced pressure to yield 2b
(14.0 g, 86.3 mmol, 86%) as a colorless liquid with a deuterium
content of Ͼ99% as determined by 1H NMR spectroscopy and
GC–MS analysis. TLC (hexane/ethyl acetate, 10:1; Rf = 0.16). GC
3-(Benzyloxy)-1-propanol (4a): Yield (10.6 g, 63.9 mmol, 63%),
TLC (hexane/ethyl acetate, 1:1; Rf = 0.38). GC (BPX-5): I = 1437.
1H NMR (400 MHz, CDCl3, TMS): δ = 7.36–7.25 (m, 5 H, 5 CH),
3
1
4.51 (s, 2 H, CH2), 4.20 (br. s, 1 H), 3.77 (t, JH,H = 5.8 Hz, JC,H
3
1
= 156.1 Hz, 2 H, CH2), 3.64 (t, JH,H = 5.9 Hz, JC,H = 141.2 Hz,
2 H, CH2), 1.85 (quint., 3JH,H = 5.8 Hz, 2 H, CH2) ppm. 13C NMR
(100 MHz, CDCl3): δ = 137.9 (Cq), 128.4 (2 CH), 127.7 (CH),
127.6 (2 CH), 73.2 (CH2), 69.0 (CH2), 61.5 (CH2), 31.9 (CH2) ppm.
MS (EI, 70 eV): m/z (%) = 166 (2) [M]+, 107 (62), 105 (10), 92 (16),
1
(BPX-5): I = 1078. H NMR (400 MHz, CDCl3, TMS): δ = 4.21
3
3
(q, JH,H = 7.2 Hz, 4 H, 2 CH2), 1.29 (t, JH,H = 7.1 Hz, 6 H, 2
CH3) ppm. 13C NMR (100 MHz, CDCl3): δ = 166.6 (2 CO), 61.4 91 (100), 79 (26), 78 (8), 77 (24), 65 (28), 63 (8), 51 (13), 39 (13).
1
(2 CH2), 41.2 (quint., JC,D = 20.2 Hz, CD2), 14.0 (2 CH3) ppm. IR (ATR): ν = 3402 (w), 3063 (w), 3031 (w), 2931 (w), 2863 (w),
˜
MS (EI, 70 eV): m/z (%) = 192 (2) [M]+, 135 (64), 117 (100), 90
1723 (m), 1495 (w), 1479 (w), 1453 (w), 1365 (w), 1178 (w), 1073
(s), 1025 (m), 912 (w), 736 (s), 697 (s), 610 (w). UV/Vis (CH2Cl2):
λmax (ε, Lmol–1 cm–1) = 258 (179), 253 (147), 227 (145) nm.
(29), 62 (23), 44 (80). IR (ATR): ν = 2982 (w), 1729 (s), 1368 (w),
˜
1247 (s), 1083 (s), 1021 (m) cm–1.
General Procedure for the Preparation of Isotopomers of Propane-
1,3-diol: As published by Lambert,[11] a 3 m solution of the respec-
tive isotopomer of diethyl malonate (2a or 2b, 1.0 equiv.) in dry
diethyl ether was added to a 1 m suspension of LiAlH4 or LiAlD4
(1.2 equiv.) in dry diethyl ether at 0 °C. The reaction mixture was
heated to reflux for 8 h and stirred overnight at room temperature.
A 1.2 m solution of NaOH (0.20 equiv.) in distilled water was added
over a period of 4 h. The precipitate was filtered, and the residue
was washed with diethyl ether and returned to the reaction flask.
Tetrahydrofuran (THF) was added, and the mixture was heated to
reflux for 30 min. Filtration was repeated, and the residue was
washed again with diethyl ether. This procedure was repeated three
times. The combined filtrates were evaporated to yield the pure
diols as yellowish oils. The deuterium content was higher than 99%
[2,2-2H2]-3-(Benzyloxy)-1-propanol (4b): Yield (5.28 g, 31.4 mmol,
47%), TLC (hexane/ethyl acetate, 2:1; Rf = 0.19). GC (BPX-5): I
= 1435. H NMR (400 MHz, CDCl3, TMS): δ = 7.37–7.25 (m, 5
1
H, 5 CH), 4.51 (s, 2 H, CH2), 3.76 (s, 2 H, CH2), 3.64 (s, 2 H,
CH2), 2.45 (s, 1 H, OH) ppm. 13C NMR (100 MHz, CDCl3): δ =
138.1 (Cq), 128.4 (2 CH), 127.7 (CH), 127.6 (2 CH), 73.2 (CH2),
1
69.1 (CH2), 61.5 (CH2), 31.4 (quint., JC,D = 19.4 Hz, CD2) ppm.
MS (EI, 70 eV): m/z (%) = 168 (4) [M]+, 149 (6), 107 (90), 91 (100),
79 (33), 65 (27) 51 (12). IR (ATR): ν = 3383 (br.), 3031 (w), 2862
˜
(w), 1092 (s), 1045 (s), 736 (s), 696 (s). UV/Vis (CH2Cl2): λmax (ε,
Lmol–1 cm–1) = 258 (162), 253 (133), 226 (79) nm.
[1,1,3,3-2H4]-3-(Benzyloxy)-1-propanol
(4c):
Yield
(3.68 g,
21.6 mmol, 45%), TLC (hexane/ethyl acetate, 2:1; Rf = 0.15). GC
1
(BPX-5): I = 1433. H NMR (400 MHz, CDCl3, TMS): δ = 7.36–
1
as determined by H NMR spectroscopy and GC–MS analysis.
[2,2-2H2]Propane-1,3-diol (3b): Yield (5.25 g, 67.0 mmol, 78%), (s, 2 H, CH2) ppm. 13C NMR (100 MHz, CDCl3): δ = 138.1 (Cq),
7.25 (m, 5 H, 5 CH), 4.51 (s, 2 H, CH2), 2.50 (s, 1 H, OH), 1.82
TLC (ethyl acetate, Rf = 0.11). GC [BPX-5, N-Methyl-N-(trimeth-
128.4 (2 CH), 127.6 (CH), 127.5 (2 CH), 73.1 (CH2), 68.3 (quint.,
1
ylsilyl)trifluoroacetamide (MSTFA)]:
I
=
1050. 1H NMR
1JC,D = 20.8 Hz, CD2), 60.7 (quint., JC,D = 21.8 Hz, CD2), 31.6
(400 MHz, CDCl3, TMS): δ = 3.85 (s, 4 H, 2 CH2), 2.27 (s, 2 H, 2 (CH2) ppm. MS (EI, 70 eV): m/z (%) = 170 (4) [M]+, 151 (5), 107
OH) ppm. 13C NMR (100 MHz, CDCl3): δ = 61.9 (2 CH2), 33.3 (81), 91 (100), 79 (34), 65 (29), 51 (16), 33 (43). IR (ATR): ν =
˜
1
(quint., JC,D = 19.2 Hz, CD2) ppm. MS (EI, 70 eV, MSTFA): m/z
3382 (br.), 3064 (w), 2935 (w), 1453 (w), 1028 (m), 735 (s), 696
(s) cm–1. UV/Vis (CH2Cl2): λmax (ε, Lmol–1 cm–1) = 258 (225), 252
(218), 230 (637) nm.
(%) = 222 (Ͻ1) [M]+, 207 (18), 177 (51), 147 (100), 132 (79), 117
(78), 103 (23), 73 (84), 59 (29), 45 (23). IR (ATR): ν = 3294 (br.),
˜
2881 (w), 1033 (s), 784 (m) cm–1.
General Procedure for the Preparation of Isotopomers of 3-(Benz-
[1,1,3,3-2H4]Propane-1,3-diol (3c): Yield (4.03 g, 50.4 mmol, 50%), yloxy)-1-propanal: To a 0.5 m solution of the respective isotopomer
TLC (ethyl acetate, Rf = 0.11). GC (BPX-5, MSTFA): I = 1045.
of 3-(benzyloxy)-1-propanol (4a–c, 1.0 equiv.) in absolute dichloro-
1H NMR (400 MHz, CDCl3, TMS): δ = 2.18 (s, 2 H, 2 OH), 1.79 methane was added pyridinium chlorochromate (1.5 equiv.). After
(s, 2 H, CH2) ppm. 13C NMR (100 MHz, CDCl3): δ = 61.2 (quint.,
1JC,D = 21.6 Hz, 2 CD2), 33.6 (CH2) ppm. MS (EI, 70 eV, MSTFA):
m/z (%) = 224 (Ͻ1) [M]+, 209 (10), 179 (25), 147 (100), 133 (50),
stirring at room temperature overnight, the reaction mixture was
filtered through silica gel and concentrated in vacuo. The residue
was purified by column chromatography on silica gel (hexane/ethyl
acetate, 3:1) to give aldehydes 5a–c as colorless liquids. A slight
loss of deuterium content was observed for compound 5b (Ͻ5%),
whereas the deuterium content was higher than 99% for compound
118 (32), 73 (47). IR (ATR): ν = 3301 (br.), 2922 (s), 2853 (s), 1457
˜
(m), 1101 (s), 801 (s) cm–1.
General Procedure for the Preparation of Isotopomers of 3-(Benz-
yloxy)-1-propanol: To a 1 m solution of sodium hydride (60% in
mineral oil, 1.3 equiv.) in absolute dimethylformamide (DMF) was
added the respective isotopomer of 1,3-propandiol (3a–c,
1.0 equiv.) at 0 °C. After stirring at 0 °C for 15 min, benzyl bromide
(1.0 equiv.) was added at 0 °C. The reaction mixture was allowed
to stir overnight at room temperature and then quenched with an
aqueous solution of HCl (2 m). The mixture was extracted with
1
5c as determined by H NMR spectroscopy and GC–MS analysis.
3-(Benzyloxy)-1-propanal (5a): Yield (8.17 g, 49.8 mmol, 78%),
TLC (hexane/ethyl acetate, 3:1; Rf = 0.38). GC (BPX-5): I = 1387.
3
1H NMR (400 MHz, CDCl3, TMS): δ = 9.78 (t, JH,H = 1.8 Hz,
1JC,H = 173.5 Hz, 1 H, CHO), 7.37–7.25 (m, 5 H, 5 CH), 4.52 (s,
3
1
1JC,H = 141.5 Hz, 2 H, CH2), 3.80 (t, JH,H = 6.0 Hz, JC,H
=
3
3
142.9 Hz, 2 H, CH2), 2.68 (td, JH,H = 6.1 Hz, JH,H = 1.9 Hz,
3342
www.eurjoc.org
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2011, 3339–3346

Synthesis of Deuterated Mevalonolactone Isotopomers
1JC,H = 126.8 Hz, 2 H, CH2) ppm. 13C NMR (100 MHz, CDCl3):
δ = 201.1 (CHO), 137.8 (Cq), 128.4 (2 CH), 127.7 (CH), 127.6 (2
[1,1,1,3,3-2H5]-4-(Benzyloxy)-2-butanol
16.2 mmol, 54%), TLC (hexane/ethyl acetate, 3:1; Rf = 0.18). GC
(6b):
Yield
(2.99 g,
1
CH), 73.2 (CH2), 63.8 (CH2), 43.8 (CH2) ppm. MS (EI, 70 eV): m/z (BPX-5): I = 1458. H NMR (400 MHz, CDCl3, TMS): δ = 7.37–
(%) = 164 (Ͻ1) [M]+, 120 (4), 107 (55), 92 (14), 91 (100), 89 (9),
7.25 (m, 5 H, 5 CH), 4.52 (s, 2 H, CH2), 3.98 (s, 1 H, CH), 3.69
3
79 (38), 78 (9), 77 (31), 65 (32), 63 (12), 51 (18), 50 (9), 39 (14). IR
(d, 3JH,H = 9.3 Hz, 1 H, CH2), 3.62 (d, JH,H = 9.4 Hz, 1 H, CH2),
(ATR): ν = 3064 (w), 3031 (w), 2865 (w), 2733 (w), 1720 (s), 1496
2.82 (s, 1 H, OH) ppm. 13C NMR (100 MHz, CDCl3): δ = 137.9
˜
(w), 1453 (w), 1394 (w), 1363 (w), 1203 (w), 1093 (s), 1027 (w), 909 (Cq), 128.4 (2 CH), 127.7 (CH), 127.6 (2 CH), 73.3 (CH2), 68.9
1
(w), 886 (w), 737 (s), 697 (s), 606 (w) cm–1. UV/Vis (CH2Cl2): λmax (CH2), 67.2 (CH), 37.5 (quint., JC,D = 19.0 Hz, CD2), 22.4 (sept.,
(ε, Lmol–1 cm–1) = 257 (214), 252 (121), 227 (179) nm.
1JC,D = 18.9 Hz, CD3) ppm. MS (EI, 70 eV): m/z (%) = 185 (Ͻ1)
[M]+, 166 (23), 120 (25), 107 (51), 91 (100), 79 (24), 65 (28), 48
[2,2-2H2]-3-(Benzyloxy)-1-propanal (5b): Yield (4.05 g, 24.4 mmol,
78%), TLC (hexane/ethyl acetate, 10:1, Rf = 0.13). GC (BPX-5): I
= 1386. 1H NMR (400 MHz, CDCl3, TMS): δ = 9.78 (s, 1 H,
CHO), 7.36–7.26 (m, 5 H, 5 CH), 4.52 (s, 2 H, CH2), 3.79 (s, 2 H,
CH2) ppm. 13C NMR (100 MHz, CDCl3): δ = 201.2 (CHO), 137.8
(Cq), 128.4 (2 CH), 127.7 (CH), 127.6 (2 CH), 73.2 (CH2), 63.7
(26). IR (ATR): ν = 3413 (br.), 3064 (w), 2931 (w), 1072 (s), 1043
˜
(s), 734 (s), 696 (s) cm–1. UV/Vis (CH2Cl2): λmax (ε, Lmol–1 cm–1)
= 228 (53) nm.
[2,4,4-2H3]-4-(Benzyloxy)-2-butanol (6c): Yield (1.95 g, 10.7 mmol,
74%), TLC (hexane/ethyl acetate, 3:1; Rf = 0.23). GC (BPX-5): I
1
1
= 1460. H NMR (400 MHz, CDCl3, TMS): δ = 7.36–7.25 (m, 5
(CH2), 43.3 (quint., JC,D = 14.1 Hz, CD2) ppm. MS (EI, 70 eV):
1
m/z (%) = 166 (Ͻ1) [M]+, 120 (3), 107 (77), 91 (100), 79 (41), 65
H, 5 CH), 4.49 (s, JC,H = 141.7 Hz, 2 H, CH2), 2.88 (br. s, 1 H,
1
OH), 1.76–1.67 (m, 2 H, CH2), 1.18 (s, JC,H = 125.3 Hz, 3 H,
(26), 51 (18). IR (ATR): ν = 3064 (w), 2862 (w), 1723 (s), 1094 (s),
˜
CH3) ppm. 13C NMR (100 MHz, CDCl3): δ = 137.6 (Cq), 128.1
(2 CH), 127.4 (CH), 127.3 (2 CH), 72.8 (CH2), 37.4 (CH2), 22.9
(CH3) ppm. MS (EI, 70 eV): m/z (%) = 183 (Ͻ1) [M]+, 164 (18),
150 (2), 122 (14), 107 (35), 91 (100), 77 (27), 65 (23), 51 (18), 42
1027 (m), 736 (s), 697 (s) cm–1. UV/Vis (CH2Cl2): λmax (ε,
Lmol–1 cm–1) = 290 (24.6), 258 (201), 252 (170), 227 (123) nm.
[1,3,3-2H3]-3-(Benzyloxy)-1-propanal (5c): Yield (2.26 g, 14.0 mmol,
63%), TLC (hexane/ethyl acetate, 10:1; Rf = 0.13). GC (BPX-5): I
(6). IR (ATR): ν = 3413 (br.), 3064 (w), 2966 (w), 2082 (w), 1453
˜
1
(w), 1144 (s), 941 (m), 696 (s) cm–1. UV/Vis (CHCl3): λmax (ε,
= 1384. H NMR (400 MHz, CDCl3, TMS): δ = 7.49–7.29 (m, 5
H, 5 CH), 4.52 (s, 2 H, CH2), 2.66 (s, 2 H, CH2) ppm. 13C NMR
Lmol–1 cm–1) = 258 (197), 253 (161), 235 (117) nm.
1
(100 MHz, CDCl3): δ = 200.8 (t, JC,D = 26.3 Hz, CDO), 137.8
[1,1,1,2,4,4-2H6]-4-(Benzyloxy)-2-butanol (6d): Yield (1.12 g,
6.02 mmol, 43%), TLC (hexane/ethyl acetate, 3:1; Rf = 0.18). GC
(Cq), 128.4 (2 CH), 127.7 (CH), 127.6 (2 CH), 73.1 (CH2), 63.0
1
(quint., JC,D = 21.9 Hz, CD2), 43.4 (CH2) ppm. MS (EI, 70 eV):
1
(BPX-5): I = 1456. H NMR (400 MHz, CDCl3, TMS): δ = 7.37–
m/z (%) = 167 (Ͻ1) [M]+, 107 (73), 91 (100), 79 (36), 65 (30), 51
7.25 (m, 5 H, 5 CH), 4.52 (s, 2 H, CH2), 2.87 (s, 1 H, OH), 1.72
(19), 39 (13). IR (ATR): ν = 3064 (w), 2858 (w), 1711 (s), 1093 (s),
˜
2
4
(dd, JH,H = 25.3 Hz, JH,H = 14.6 Hz, 2 H, CH2) ppm. 13C NMR
(100 MHz, CDCl3): δ = 137.9 (Cq), 128.4 (2 CH), 127.7 (CH),
127.6 (2 CH), 73.2 (CH2), 68.2 (quint., 1JC,D = 21.9 Hz, CD2), 66.8
736 (s), 697 (s) cm–1. UV/Vis (CH2Cl2): λmax (ε, Lmol–1 cm–1) = 258
(188), 253 (152), 226 (83) nm.
1
1
(t, JC,D = 22.1 Hz, CD), 37.7 (CH2), 22.1 (sept., JC,D = 19.2 Hz,
General Procedure for the Preparation of Isotopomers of 4-(Benz-
yloxy)-2-butanol: To a 0.5 m solution of methylmagnesium iodide/
[2H3]methylmagnesium iodide in absolute diethyl ether, prepared
from methyl iodide/[2H3]methyl iodide (1.1 equiv.) and Mg
(1.1 equiv.) was added a 2 m solution of the respective isotopomer
of 3-(benzyloxy)-1-propanal (5a–c, 1.0 equiv.) in absolute diethyl
ether at 0 °C. After stirring at room temperature for 1 h, the reac-
tion mixture was quenched with a saturated solution of NH4Cl and
then extracted with Et2O. The organic layer was dried with MgSO4
and concentrated in vacuo. The residue was purified by column
chromatography on silica gel (hexane/ethyl acetate, 3:1) to give
alcohols 6a–d as colorless liquids. No loss of deuterium content
CD3) ppm. MS (EI, 70 eV): m/z (%) = 186 (Ͻ1) [M]+, 167 (12), 122
(12), 107 (28), 91 (100), 77 (29), 65 (30), 49 (51). IR (ATR): ν =
˜
3396 (br.), 3064 (w), 2932 (w), 1172 (m), 1101 (s), 736 (s), 696
(s) cm–1. UV/Vis (CH2Cl2): λmax (ε, Lmol–1 cm–1) = 257 (239), 252
(244), 230 (591) nm.
General Procedure for the Preparation of Isotopomers of 4-(Benz-
yloxy)-2-butanone: To a 0.2 m solution of the respective isotopomer
of 4-(benzyloxy)-2-butanol (6a–d, 1.0 equiv.) in absolute dichloro-
methane was added pyridinium chlorochromate (1.5 equiv.). After
stirring at room temperature for 4 h, the reaction mixture was fil-
tered, and the filtrate was concentrated in vacuo. The residue was
purified by column chromatography on silica gel (hexane/ethyl
acetate, 5:1) to give methyl ketones 7a–d as colorless liquids. No
1
was observed by H NMR spectroscopy or GC–MS analysis.
[1,1,1-2H3]-4-(Benzyloxy)-2-butanol (6a): Yield (4.42 g, 24.2 mmol,
70%) TLC (hexane/ethyl acetate, 3:1; Rf = 0.21). GC (BPX-5): I =
1
loss of deuterium content was observed by H NMR spectroscopy
or GC–MS analysis.
1
1462. H NMR (400 MHz, CDCl3, TMS): δ = 7.36–7.25 (m, 5 H,
1
3
5 CH), 4.52 (s, JC,H = 141.7 Hz, 2 H, CH2), 3.99 (dd, JH,H
=
[1,1,1-2H3]-4-(Benzyloxy)-2-butanone
21.1 mmol, 93%), TLC (Rf = 0.21). GC (BPX-5): I = 1463. 1H
(7a):
Yield
(3.82 g,
8.1 Hz, 3JH,H = 2.7 Hz, 1 H, CH), 3.70 (ddd, 3JH,H = 9.4 Hz, 3JH,H
3
3
= 5.6 Hz, JH,H = 4.9 Hz, 1 H, CH2), 3.63 (ddd, JH,H = 9.4 Hz, NMR (400 MHz, CDCl3, TMS): δ = 7.36–7.25 (m, 5 H, 5 CH),
3JH,H = 7.9 Hz, JH,H = 4.7 Hz, 1 H, CH2), 2.90 (br. s, 1 H, OH),
4.50 (s, 1JC,H = 141.4 Hz, 2 H, CH2), 3.73 (t, 3JH,H = 6.3 Hz, JC,H
3
1
1.81–1.67 (m, 2 H, CH2) ppm. 13C NMR (100 MHz, CDCl3): δ =
= 143.3 Hz, 2 H, CH2), 2.70 (t, JH,H = 6.3 Hz, JC,H = 126.0 Hz,
3
1
137.9 (Cq), 128.4 (2 CH), 127.7 (CH), 127.6 (2 CH), 73.2 (CH2),
2 H, CH2) ppm. 13C NMR (100 MHz, CDCl3): δ = 207.2 (CO),
69.1 (CH2), 67.3 (CH), 38.1 (CH2) ppm. MS (EI, 70 eV): m/z (%) 138.0 (Cq), 128.3 (2 CH), 127.6 (3 CH), 73.2 (CH2), 65.2 (CH2),
= 183 (Ͻ1) [M]+, 161 (11), 120 (11), 108 (9), 107 (30), 105 (12), 92 43.7 (CH2) ppm. MS (EI, 70 eV): m/z (%) = 181 (Ͻ1) [M]+, 120
(14), 91 (100), 89 (8), 79 (21), 78 (9), 77 (23), 65 (29), 63 (8), 59 (9), (12), 107 (35), 92 (11), 91 (82), 89 (8), 79 (20), 78 (9), 77 (25), 75
51 (13), 48 (36), 46 (17), 43 (9), 39 (10). IR (ATR): ν = 3409 (w),
(11), 65 (29), 63 (9), 57 (8), 51 (15), 46 (100), 39 (12). IR (ATR): ν
˜
˜
3064 (w), 3031 (w), 2915 (w), 2862 (w), 2222 (w), 1453 (w), 1363
(w), 1206 (w), 1089 (s), 1028 (m), 909 (w), 736 (s), 697 (s), 610 (m),
= 3064 (w), 3031 (w), 2866 (w), 1708 (s), 1496 (w), 1453 (w), 1365
(m), 1250 (w), 1179 (m), 1100 (s), 1074 (s), 1026 (m), 737 (s), 698
553 (w) cm–1. UV/Vis (CH2Cl2): λmax (ε, Lmol–1 cm–1) = 258 (202), (s), 610 (w), 543 (w) cm–1. UV/Vis (CH2Cl2): λmax (ε, Lmol–1 cm–1)
252 (174), 226 (125) nm.
= 258 (195), 253 (161), 227 (171) nm.
Eur. J. Org. Chem. 2011, 3339–3346
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3343

J. S. Dickschat, C. A. Citron, N. L. Brock, R. Riclea, H. Kuhz
FULL PAPER
1
[1,1,1,3,3-2H5]-4-(Benzyloxy)-2-butanone (7b): Yield (2.30 g,
12.6 mmol, 78%), TLC (hexane/ethyl acetate, 5:1; Rf = 0.24). GC
= 7.1 Hz, JC,H = 127.1 Hz, 3 H, CH3) ppm. 13C NMR (100 MHz,
CDCl3): δ = 172.4 (CO), 137.9 (Cq), 128.3 (2 CH), 127.6 (3 CH),
73.2 (CH2), 70.6 (Cq), 66.7 (CH2), 60.4 (CH2), 45.4 (CH2), 40.3
1
(BPX-5): I = 1458. H NMR (400 MHz, CDCl3, TMS): δ = 7.36–
7.26 (m, 5 H, 5 CH), 4.51 (s, 2 H, CH2), 3.72 (s, 2 H, CH2) ppm. (CH2), 14.1 (CH3) ppm. MS (EI, 70 eV): m/z (%) = 269 (Ͻ1) [M]
13C NMR (100 MHz, CDCl3): δ = 207.5 (CO), 138.0 (Cq), 128.4 +, 163 (17), 145 (11), 134 (8), 92 (11), 91 (100), 88 (12), 79 (11), 77
(2 CH), 127.64 (2 CH), 127.62 (CH), 73.2 (CH2), 65.1 (CH2), 43.1
(12), 72 (8), 65 (16), 46 (23). IR (ATR): ν = 3498 (w), 3064 (w),
˜
1
1
(quint., JC,D = 19.2 Hz, CD2), 29.7 (sept., JC,D = 19.4 Hz,
3031 (w), 2981 (w), 2936 (w), 2867 (w), 2229 (w), 1728 (s), 1454
(w), 1369 (m), 1333 (w), 1193 (s), 1096 (s), 1026 (s), 907 (w), 850
(w), 736 (s), 698 (s), 598 (w) cm–1. UV/Vis (CH2Cl2): λmax (ε,
Lmol–1 cm–1) = 258 (243), 252 (220), 227 (298) nm.
CD3) ppm. MS (EI, 70 eV): m/z (%) = 183 (Ͻ1) [M]+, 120 (18), 107
(86), 91 (100), 77 (56), 65 (49), 46 (99). IR (ATR): ν = 3064 (w),
˜
2865 (w), 1706 (s), 1207 (m), 1094 (s), 737 (s), 689 (s) cm–1. UV/
Vis (CH2Cl2): λmax (ε, Lmol–1 cm–1) = 258 (215), 252 (199), 227
(137) nm.
Ethyl [4,4,6,6,6-2H5]-5-(Benzyloxy)-3-hydroxy-3-methylpentanoate
(8b): Yield (2.69 g, 9.93 mmol, 79%), TLC (hexane/ethyl acetate,
[4,4-2H2]-4-(Benzyloxy)-2-butanone (7c): Yield (1.40 g, 7.74 mmol, 4:1; Rf = 0.20). GC (BPX-5): I = 1915. 1H NMR (400 MHz,
74%) TLC (hexane/ethyl acetate, 3:1; Rf = 0.34). GC (BPX-5): I = CDCl3, TMS): δ = 7.37–7.25 (m, 5 H, 5 CH), 4.49 (s, 2 H, CH2),
1
2
3
1463. H NMR (400 MHz, CDCl3, TMS): δ = 7.35–7.25 (m, 5 H, 4.15 (dq, JH,H = 10.8 Hz, JH,H = 7.2 Hz, 1 H, CH2), 4.12 (dq,
1
1
3
5 CH), 4.50 (s, JC,H = 141.6 Hz, 2 H, CH2), 2.69 (s, JC,H
=
2JH,H = 10.8 Hz, JH,H = 7.1 Hz, 1 H, CH2), 3.95 (br. s, 1 H, OH),
1
2
125.0 Hz, 2 H, CH2), 2.17 (s, JC,H = 127.3 Hz, 3 H, CH3) ppm.
3.67 (s, 2 H, CH2), 2.57 (d, JH,H = 15.2 Hz, 1 H, CH2), 2.49 (d,
13C NMR (100 MHz, CDCl3): δ = 207.1 (CO), 138.0 (Cq), 128.3 2JH,H = 15.3 Hz, 1 H, CH2), 1.24 (t, JH,H = 7.2 Hz, 3 H,
3
(2 CH), 127.63 (2 CH), 127.61 (CH), 73.1 (CH2), 43.5 (CH2), 30.4
(CH3) ppm. MS (EI, 70 eV): m/z (%) = 180 (Ͻ1) [M]+, 122 (12),
107 (65), 91 (100), 79 (34), 65 (29), 51 (18), 43 (84). IR (ATR):
3064 (w), 2856 (w), 1714 (s), 1361 (m), 1102 (s), 698 (s) cm–1. UV/
CH3) ppm. 13C NMR (100 MHz, CDCl3): δ = 172.1 (CO), 137.6
(Cq), 128.0 (2 CH), 127.32 (CH), 127.31 (2 CH), 72.9 (CH2), 70.2
(Cq), 66.5 (CH2), 60.1 (CH2), 45.1 (CH2), 13.8 (CH3) ppm. MS
(EI, 70 eV): m/z (%) = 253 (Ͻ1) [M – H2O]+, 184 (1), 165 (21), 147
Vis (CHCl3): λmax (ε, Lmol–1 cm–1) = 258 (207), 253 (170), 233 (12), 134 (8), 115 (5), 107 (6), 91 (100), 74 (10), 65 (11), 46 (19).
(121) nm.
Ethyl [5,5-2H2]-5-(Benzyloxy)-3-hydroxy-3-methylpentanoate (8c):
[1,1,1,4,4-2H5]-4-(Benzyloxy)-2-butanone (7d): Yield (739 mg,
4.04 mmol, 67%), TLC (hexane/ethyl acetate, 5:1; Rf = 0.24). GC
Yield (528 mg, 1.97 mmol, 60%), TLC (hexane/ethyl acetate, 4:1;
Rf = 0.14). GC (BPX-5): I = 1921. 1H NMR (400 MHz, CDCl3,
TMS): δ = 7.36–7.26 (m, 5 H, 5 CH), 4.50 (s, 2 H, CH2), 4.15 (dq,
1
(BPX-5): I = 1458. H NMR (400 MHz, CDCl3, TMS): δ = 7.36–
7.25 (m, 5 H, 5 CH), 4.51 (s, 2 H, CH2), 2.70 (s, 2 H, CH2) ppm. 2JH,H = 10.8 Hz, JH,H = 7.1 Hz, 1 H, CH2), 4.12 (dq, JH,H
=
3
2
13C NMR (100 MHz, CDCl3): δ = 207.3 (CO), 138.0 (Cq), 128.3 10.9 Hz, 3JH,H = 7.1 Hz, 1 H, CH2), 3.97 (br. s, 1 H, OH), 2.57 (d,
1
1
2
(2 CH), 127.6 (2 CH), 127.6 (CH), 64.5 (quint., JC,D = 21.8 Hz,
2JH,H = 15.2 Hz, JC,H = 129.3 Hz, 1 H, CH2), 2.49 (d, JH,H
=
CD2), 43.5 (CH2), 29.7 (sept., 1JC,D = 19.4 Hz, CD3) ppm. MS (EI, 15.2 Hz, JC,H = 128.4 Hz, 1 H, CH2), 1.92 (d, JH,H = 14.9 Hz, 1
1
2
70 eV): m/z (%) = 183 (8) [M]+, 165 (2), 122 (36), 107 (100), 91 H, CH2), 1.87 (d, JH,H = 14.8 Hz, 1 H, CH2), 1.28 (s, JC,H
=
2
1
3
(92), 77 (18). IR (ATR): ν = 3064 (w), 2858 (w), 1708 (s), 1164 (m),
127.0 Hz, 3 H, CH3), 1.25 (t, JH,H = 7.2 Hz, 3 H, CH3) ppm. 13C
˜
1099 (s), 737 (s), 698 (s) cm–1. UV/Vis (CH2Cl2): λmax (ε, NMR (100 MHz, CDCl3): δ = 172.4 (CO), 138.0 (Cq), 128.4 (2
Lmol–1 cm–1) = 258 (204), 252 (174), 227 (151) nm.
CH), 127.7 (CH), 127.6 (2 CH), 73.1 (CH2), 70.7 (Cq), 65.2 (Cq),
60.6 (CH2), 45.5 (CH2), 40.1 (CH2), 27.1 (CH3), 14.1 (CH3) ppm.
MS (EI, 70 eV): m/z (%) = 268 (Ͻ1) [M]+, 181 (3), 142 (46), 144
(24), 131 (18), 107 (17), 91 (100), 77 (28), 65 (34), 43 (63). IR
General Procedure for the Preparation of Isotopomers of Ethyl 5-
(Benzyloxy)-3-hydroxy-3-methylpentanoate: To a 2 m solution of
naphthalene (3 equiv.) in absolute THF was added lithium
(3 equiv.). After consumption of the lithium, a 1 m suspension of
ZnCl2 (1.5 equiv.) in absolute THF was added dropwise to the
green solution. Stirring was continued for 30 min, and then a 2 m
solution of the respective isotopomer of 4-(benzyloxy)-2-butanone
(7a–d, 1.0 equiv.) in absolute THF and ethyl bromoacetate
(1.3 equiv.) was added dropwise. The reaction was stirred at room
temperature for 3 h and quenched with a saturated solution of
aqueous NH4Cl. After extracting with diethyl ether, the organic
layer was dried with MgSO4 and concentrated in vacuo. The resi-
due was purified by column chromatography on silica gel (hexane/
ethyl acetate, 4:1) to give esters 8a–d as colorless liquids. No loss
of deuterium content was observed by 1H NMR spectroscopy or
GC–MS analysis.
(ATR): ν = 3497 (br.), 2978 (w), 2080 (w), 1727 (s), 1372 (m), 1193
˜
(s), 698 (s). UV/Vis (CHCl3): λmax (ε, Lmol–1 cm–1) = 258 (285),
252 (260), 239 (234) nm.
Ethyl [5,5,6,6,6-2H5]-5-(Benzyloxy)-3-hydroxy-3-methylpentanoate
(8d): Yield (540 mg, 1.85 mmol, 62%), TLC (hexane/ethyl acetate,
5:1; Rf = 0.15). GC (BPX-5): I = 1917. 1H NMR (400 MHz,
CDCl3, TMS): δ = 7.36–7.26 (m, 5 H, 5 CH), 4.50 (s, 2 H, CH2),
2
3
4.15 (dq, JH,H = 10.8 Hz, JH,H = 7.2 Hz, 1 H, CH2), 4.11 (dq,
2JH,H = 10.8 Hz, JH,H = 7.0 Hz, 1 H, CH2), 2.57 (d, JH,H
=
3
2
2
15.3 Hz, 1 H, CH2), 2.49 (d, JH,H = 15.2 Hz, 1 H, CH2), 1.92 (d,
2JH,H = 14.8 Hz, 1 H, CH2), 1.87 (d, JH,H = 14.8 Hz, 1 H, CH2),
2
1.25 (t, JH,H = 7.2 Hz, 3 H, CH3) ppm. 13C NMR (100 MHz,
3
CDCl3): δ = 172.7 (CO), 138.3 (Cq), 128.7 (2 CH), 127.9 (CH),
1
127.9 (2 CH), 73.4 (CH2), 70.9 (Cq), 66.4 (quint., JC,D = 21.6 Hz,
Ethyl [6,6,6-2H3]-5-(Benzyloxy)-3-hydroxy-3-methylpentanoate (8a):
Yield (1.42 g, 5.28 mmol, 70%), TLC (hexane/ethyl acetate, 4:1; Rf
= 0.20). GC (BPX-5): I = 1918. 1H NMR (400 MHz, CDCl3,
TMS): δ = 7.36–7.25 (m, 5 H, 5 CH), 4.50 (s, 2 H, CH2), 4.15 (dq,
CD2), 60.7 (CH2), 45.8 (CH2), 40.4 (CH2), 14.4 (CH3) ppm. MS
(EI, 70 eV): m/z (%) = 271 (Ͻ1) [M]+, 165 (19), 147 (12), 134 (6),
107 (6), 91 (100), 77 (11), 65 (13). IR (ATR): ν = 3493 (br.), 3064
˜
(w), 2938 (w), 1728 (s), 1195 (s), 1026 (s), 736 (s), 697 (s) cm–1. UV/
Vis (CH2Cl2): λmax (ε, Lmol–1 cm–1) = 257 (285), 252 (296), 228
(433) nm.
2JH,H = 10.8 Hz, JH,H = 7.2 Hz, 1 H, CH2), 4.12 (dq, JH,H
=
3
2
3
10.9 Hz, JH,H = 7.1 Hz, 1 H, CH2), 3.95 (br. s, 1 H), 3.69 (dt,
2JH,H = 9.8 Hz, 3JH,H = 6.1 Hz, 1 H, CH2), 3.66 (dt, 2JH,H = 9.9 Hz,
3JH,H = 6.2 Hz, 1 H, CH2), 2.57 (d, JH,H = 15.3 Hz, JC,H
=
General Procedure for the Preparation of Isotopomers of Mevalono-
2
1
2
1
129.4 Hz, 1 H, CH2), 2.50 (d, JH,H = 15.3 Hz, JC,H = 128.6 Hz, lactone: A 0.1 m solution of the respective isotopomer of 5-(benz-
2
3
1 H, CH2), 1.93 (dt, JH,H = 14.4 Hz, JH,H = 6.1 Hz, 1 H, CH2),
yloxy)-3-hydroxy-3-methylpentanoate (8a–d, 1.0 equiv.) was dis-
1.88 (dt, 2JH,H = 14.5 Hz, 3JH,H = 6.3 Hz, 1 H, CH2), 1.25 (t, 3JH,H solved in diethyl ether and a catalytic amount of Pd/C (10 wt.%
3344
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Eur. J. Org. Chem. 2011, 3339–3346

Synthesis of Deuterated Mevalonolactone Isotopomers
Pd, 0.05 equiv.) was added. The mixture was stirred in a high pres-
sure reactor (HR-100, Berghof, Eningen) under a hydrogen atmo-
sphere (35 bar) at 40 °C until all of the starting material was con-
sumed (90 min). The mixture was filtered through silica gel to give
the deprotected alcohols as colorless oils. This crude material was
dissolved in dichloromethane to give a 0.1 m solution, and p-tolu-
enesulfonic acid (0.10 equiv.) was added. The mixture was stirred
overnight and concentrated in vacuo. Column chromatography on
silica gel (diethyl ether) gave the mevalonolactones 1a–d as color-
CD3) ppm. MS (EI, 70 eV, MSTFA): m/z (%) = 207 (Ͻ1) [M]+, 192
(13), 160 (6), 150 (100), 118 (65), 102 (7), 73 (30) 45 (16). IR (ATR):
ν = 3418 (br.), 1704 (s), 1292 (s) 1156 (m), 1102 (s), 871 (m) cm–1.
˜
[2,2,6,6,6-2H5]-5-(Benzyloxy)-3-hydroxy-3-methylpentanenitrile (8e):
To a solution of diisopropylamine (2.70 g, 26.7 mmol, 1.1 equiv.)
in anhydrous THF (25 mL) under nitrogen was added dropwise
nBuLi (1.6 m in hexane, 16.7 mL, 26.7 mmol, 1.1 equiv.) at 0 °C.
After stirring at 0 °C for 1 h, the reaction mixture was cooled to
–90 °C.
A
solution of [2H3]acetonitrile (1.07 g, 24.3 mmol,
1
less oils. No loss of deuterium content was observed by H NMR
1.0 equiv.) in anhydrous THF (15 mL) was added followed by ad-
dition of the ketone (7a, 4.44 g, 24.3 mmol, 1.0 equiv.). The reac-
tion mixture was stirred at –90 °C for 1 h and then warmed to room
temperature overnight. The mixture was hydrolyzed by the addition
of an aqueous saturated solution of NH4Cl. The aqueous layer was
extracted with diethyl ether (3ϫ), the organic phase was dried with
MgSO4, and the solvents were evaporated. The crude product was
purified by column chromatography on silica gel with hexane/ethyl
acetate (5:1) to give 8e (4.45 g, 19.9 mmol, 82%) as a pale yellow
liquid and with a deuterium content of Ͼ99% determined by 1H
NMR spectroscopy and GC–MS analysis. TLC (hexane/ethyl acet-
spectroscopy or GC–MS analysis.
[6,6,6-2H3]Mevalonolactone (1a): Yield (378 mg, 2.84 mmol, 59%),
TLC (diethyl ether, Rf = 0.15). GC (BPX-5, MSTFA): I = 1388.
1H NMR (400 MHz, CDCl3, TMS): δ = 4.62 (ddd, JH,H
=
2
3
3
11.3 Hz, JH,H = 8.0 Hz, JH,H = 6.8 Hz, 1 H, CH2), 4.35 (ddd,
2JH,H = 11.3 Hz, JH,H = 4.7 Hz, JH,H = 4.4 Hz, 1 H, CH2), 3.05
(br. s, 1 H, OH), 2.66 (dt, JH,H = 17.4 Hz, JH,H = 1.3 Hz, 1 H,
CH2), 2.50 (d, JH,H = 17.4 Hz, 1 H, CH2), 1.93–1.91 (m, 1 H,
3
3
2
4
2
3
4
CH2), 1.90 (dd, JH,H = 4.6 Hz, JH,H = 1.3 Hz, 1 H, CH2) ppm.
13C NMR (100 MHz, CDCl3): δ = 171.2 (CO), 67.7 (Cq), 66.2
1
1
ate, 1:1; Rf = 0.45). GC (BPX-5): I = 1822. H NMR (400 MHz,
(CH2), 44.4 (CH2), 35.5 (CH2), 28.6 (sept., JC,D = 19.3 Hz,
1
CD3) ppm. MS (EI, 70 eV, MSTFA): m/z (%) = 205 (Ͻ1) [M]+, 190
(9), 149 (13), 148 (100), 147 (29), 119 (10), 118 (2), 117 (12), 101
(12), 76 (28), 75 (44), 74 (10), 73 (50), 61 (9), 59 (14), 58 (14), 47
(13), 46 (28), 45 (35), 44 (15), 43 (25), 42 (32), 41 (12). IR (ATR):
CDCl3, TMS): δ = 7.38–7.27 (m, 5 H, 5 CH), 4.52 (s, JC,H
=
142.2 Hz, 2 H, CH2), 3.87 (br. s, 1 H, OH), 3.79–3.69 (m, 2 H,
2
3
3
CH2), 1.99 (ddd, JC,H = 14.9 Hz, JC,H = 7.2 Hz, JC,H = 4.3 Hz,
2
3
3
1 H, CH2), 1.89 (ddd, JC,H = 14.9 Hz, JC,H = 6.9 Hz, JC,H
=
4.4 Hz, 1 H, CH2) ppm. 13C NMR (100 MHz, CDCl3): δ = 137.1
ν = 3420 (w), 2974 (w), 2922 (w), 2227 (w), 1716 (s), 1474 (w), 1399
˜
(Cq), 128.5 (2 CH), 128.0 (CH), 127.8 (2 CH), 117.6 (CN), 73.5
(m), 1305 (w), 1263 (s), 1228 (s), 1172 (m), 1140 (w), 1108 (s), 1071
(s), 1021 (w), 998 (s), 976 (m), 931 (w), 883 (w), 821 (m), 787 (w),
731 (m), 652 (m), 575 (m) cm–1. The 1H and 13C NMR spectro-
scopic data closely resembled those reported previously.[6c]
1
(CH2), 70.7 (Cq), 66.7 (CH2), 38.8 (CH2), 30.4 (quint., JC,D
20.4 Hz, CD2), 26.1 (quint., JC,D = 19.5 Hz, CD2) ppm. MS (EI,
=
1
70 eV): m/z (%) = 224 (4) [M]+, 195 (1), 182 (1), 163 (1), 119 (4),
107 (49), 91 (100), 79 (23), 65 (24), 46 (33), 39 (7). IR (ATR): ν =
˜
[4,4,6,6,6-2H5]Mevalonolactone (1b): Yield (1.14 g, 8.44 mmol,
85%) TLC (ethyl acetate, Rf = 0.10). GC (BPX-5, MSTFA): I =
3467 (br.), 3064 (w), 3032 (w), 2920 (w), 2869 (w), 2250 (w), 1496
(w), 1454 (w), 1416 (w), 1366 (m), 1097 (s), 1046 (m), 854 (w), 815
(w), 740 (m), 699 (m) cm–1. UV/Vis (CH2Cl2): λmax (ε, Lmol–1 cm–1)
2
1385. 1H NMR (400 MHz, CDCl3, TMS): δ = 4.60 (d, JH,H
=
2
11.3 Hz, 1 H, CH2), 4.34 (d, JH,H = 11.3 Hz, 1 H, CH2), 2.71 (br.
=
227 (200), 258 (180) nm. HRMS (EI, 70 eV): calcd. for
2
2
s, 1 H, OH), 2.66 (d, JH,H = 17.4 Hz, 1 H, CH2), 2.52 (d, JH,H
=
C13H12D5NO2 [M]+ 224.15676; found 224.15669.
17.3 Hz, 1 H, CH2) ppm. 13C NMR (100 MHz, CDCl3): δ = 170.5
(CO), 68.0 (Cq), 65.9 (CH2), 44.6 (CH2) ppm. MS (EI, 70 eV,
MSTFA): m/z (%) = 207 (Ͻ1) [M]+, 192 (12), 162 (11), 150 (100),
[2,2,6,6,6-2H5]mevalonolactone (1e): Compound 8e (4.41 g,
19.7 mmol) was added to a suspension of Pd/Al2O3 (2.09 g,
1.96 mmol, 10 wt.% Pd) in ethanol (40 mL) in the presence of wet
acetic acid (2 mL). The reaction was carried out in a stainless steel
autoclave (HR-100, Berghof, Eningen) equipped with a magnetic
stirrer in a hydrogen atmosphere at 60 °C. When no starting mate-
rial was detected by TLC or GC analysis, the mixture was filtered
and concentrated. Due to its instability, the crude product (1.62 g)
was used immediately and without further purification in the next
reaction. The oil was dissolved in D2O (15 mL). To the mixture
was added a solution of NaOD in D2O (1.50 g, 40 wt.%, 15 mmol)
and stirred for 20 h. The mixture was acidified with HCl (2 n), and
the mixture was concentrated. The resulting residue was purified
by column chromatography on silica gel with hexane/ethyl acetate
(1:1) to give 1e (1.23 g, 9.11 mmol, 46%) with no detectable loss of
deuterium by 1H NMR spectroscopy and GC–MS analysis. TLC
(hexane/ethyl acetate, 1:1; Rf = 0.12). GC (BPX-5, MSTFA): I =
133 (5), 118 (44), 103 (11), 73 (39), 59 (6), 46 (15). IR (ATR): ν =
˜
3417 (br.), 2974 (w), 2917 (w), 1704 (s), 1398 (m), 1240 (s), 1041
(s), 859 (m) cm–1. The 1H and 13C NMR spectroscopic data closely
matched those reported previously.[9]
[5,5-2H2]Mevalonolactone (1c): Yield (169 mg, 1.28 mmol, 70%),
TLC (ethyl acetate, Rf = 0.13). GC (BPX-5, MSTFA): I = 1387.
1H NMR (400 MHz, CDCl3, TMS): δ = 2.71 (br. s, 1 H, OH), 2.66
2
4
4
1
(ddd, JH,H = 17.4 Hz, JH,H = 1.7 Hz, JH,H = 1.2 Hz, JC,H
=
2
2
133.0 Hz, 1 H, CH2), 2.51 (d, JH,H = 17.4 Hz, JC,H = –6.9 Hz, 1
H, CH2), 1.92 (d, JH,H = 14.7 Hz, JC,H = 128.6 Hz, 1 H, CH2),
2
1
2
1
1.88 (d, JH,H = 14.7 Hz, JC,H = 128.6 Hz, 1 H, CH2), 1.39 (s,
1JC,H = 126.2 Hz, 3 H, CH3) ppm. 13C NMR (100 MHz, CDCl3):
δ = 171.0 (CO), 68.0 (Cq), 65.5 (quint., 1JC,D = 23.2 Hz, CD2), 44.6
(CH2), 35.6 (CH2), 29.7 (CH3) ppm. MS (EI, 70 eV, MSTFA): m/z
(%) = 204 (Ͻ1) [M]+, 189 (13), 157 (5), 147 (100), 115 (77), 75 (54),
1
2
1384. H NMR (400 MHz, CDCl3, TMS): δ = 4.58 (ddd, JC,H
=
=
59 (13), 43 (36). IR (ATR): ν = 3418 (br.), 2969 (w), 1704 (s), 1260
˜
3
3
2
11.3 Hz, JC,H = 8.4 Hz, JC,H = 6.4 Hz, 1 H, CH2), (ddd, JC,H
(s), 1120 (s), 1024 (s), 861 (m) cm–1.
3
3
11.3 Hz, JC,H = 5.0 Hz, JC,H = 4.2 Hz, 1 H, CH2), 2.75 (br. s, 1
[5,5,6,6,6-2H5]Mevalonolactone (1d): Yield (130 mg, 0.96 mmol, H, OH), 1.89 (dd, JC,H = 2.9, JC,H = 5.1 Hz, 1 H, CH2), 1.88 (d,
3
3
52%) TLC (diethyl ether, Rf = 0.10). GC (BPX-5, MSTFA): I =
3JC,H = 4.6 Hz, 1 H, CH2) ppm. 13C NMR (100 MHz, CDCl3): δ
1
1
1385. H NMR (400 MHz, CDCl3, TMS): δ = 2.98 (s, 1 H, OH), = 171.0 (CO), 67.8 (Cq), 66.1 (CH2), 43.9 (quint., JC,D = 20.5 Hz,
2.66 (dt, 2JH,H = 17.5 Hz, 4JH,H = 1.4 Hz, 1 H, CH2), 2.50 (d, 2JH,H
CD2), 35.7 (CH2), 28.7 (sept., 1JC,D = 18.6 Hz, CD3) ppm. MS (EI,
= 17.4 Hz, 1 H, CH2), 1.90 (s, 2 H, CH2) ppm. 13C NMR 70 eV, MSTFA): m/z (%) = 192 (10), 162 (6), 148 (100), 135 (4),
(100 MHz, CDCl3): δ = 171.2 (CO), 67.7 (Cq), 65.6 (quint., 1JC,D
22.9 Hz, CD2), 44.5 (CH2), 35.4 (CH2), 28.6 (sept., 1JC,D = 19.5 Hz,
=
118 (37), 101 (11), 73 (31), 59 (6), 46 (16). IR (ATR): ν = 3415
˜
(br.), 2974 (w), 2924 (w), 2227 (w), 1714 (s), 1475 (w), 1407 (m),
Eur. J. Org. Chem. 2011, 3339–3346
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3345

J. S. Dickschat, C. A. Citron, N. L. Brock, R. Riclea, H. Kuhz
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Acknowledgments
This work was funded by an Emmy Noether fellowship from the
Deutsche Forschungsgemeinschaft (DFG) (grant to J. S. D.), a
scholarship from the Fonds der Chemischen Industrie (to N. L. B),
and a gift of solvents from BASF AG, Ludwigshafen. We thank
Prof. Dr. Stefan Schulz for his excellent support.
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Received: February 9, 2011
Published Online: May 5, 2011
3346
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Eur. J. Org. Chem. 2011, 3339–3346