Regioselective synthesis of 1,3,5-13 C3 and 2,4-13 C2-labeled 2-deoxyribonolactones

Article abstract of DOI:10.1081/NCN-100108326

The synthesis of 1,3,5-¹³ C_3- and 2,4-¹³ C₂-labeled 5-0-bromobenzyl2-deoxyribonolactones 2, precursors to ¹³C-enriched nucleoside phosphoramidites for solid-phase synthesis of DNA oligonucletides, is

Full text of DOI:10.1081/NCN-100108326

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REGIOSELECTIVE SYNTHESIS OF 1,3,5-13C3 AND
2,4-13C2-LABELED 2-DEOXYRIBONOLACTONES
Paul J. Hatala a , James Kallmerten b & Philip N. Borer c
a Department of Chemistry , Syracuse University , Syracuse, NY, 13244-4100, U.S.A.
b Department of Chemistry , Syracuse University , Syracuse, NY, 13244-4100, U.S.A.
c Department of Chemistry , Syracuse University , Syracuse, NY, 13244-4100, U.S.A.
Published online: 17 Aug 2006.
To cite this article: Paul J. Hatala , James Kallmerten & Philip N. Borer (2001) REGIOSELECTIVE SYNTHESIS OF 1,3,5-13C3 AND
2,4-13C2-LABELED 2-DEOXYRIBONOLACTONES, Nucleosides, Nucleotides and Nucleic Acids, 20:12, 1961-1973
To link to this article: http://dx.doi.org/10.1081/NCN-100108326
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NUCLEOSIDES, NUCLEOTIDES & NUCLEIC ACIDS, 20(12), 1961–1973 (2001)
REGIOSELECTIVE SYNTHESIS OF 1,3,5-13C3 AND
2,4-13C2-LABELED 2-DEOXYRIBONOLACTONES
Paul J. Hatala, James Kallmerten,* and Philip N. Borer*
Department of Chemistry, Syracuse University, Syracuse,
NY 13244-4100, USA
ABSTRACT
The synthesis of 1,3,5-13C3- and 2,4-13C2-labeled 5-O-bromobenzyl-
2-deoxyribonolactones 2, precursors to 13C-enriched nucleoside phospho-
ramidites for solid-phase synthesis of DNA oligonucletides, is described.
An equimolar combination of these two multiply labeled lactones affords
a ‘‘population-labeled’’ mixture of isotopomers which exhibits an
approximately 50-fold increase in the sensitivity of 13C-NMR compared
to natural abundance measurements. The 13C-13C 2-bond and 4-bond
coupling constants are reported for the lactones; all are < 2Hz, con-
firming that this labeling scheme should be especially useful for NMR-
relaxation measurements.
INTRODUCTION
As part of our ongoing effort to investigate the structure and dynamics
of DNA oligomers1, we recently reported the preparation of the series of
regioselectively 13C1-deoxyribonolactones2. These labeled deoxyribose deri-
vatives are pivotal intermediates in a novel strategy for 13C labeling of syn-
thetic oligonucleotides, in which a 13C-enriched oligonucleotide is prepared
from phophoramidite monomers which are themselves synthesized from
equimolar mixtures of the 13C1-labeled isotopomers of deoxyribose. Each
*Corresponding authors.
1961
Copyright # 2001 by Marcel Dekker, Inc.
www.dekker.com

1962
HATALA, KALLMERTEN, AND BORER
deoxyribose subunit of the oligonucleotide derived from such ‘‘population
labeled’’ precursors will contain a single, randomly distributed 13C atom,
resulting in a net 13C enrichment of approximately 21% at each of the carbon
atoms of the phosphodeoxyribose backbone.
The success of our synthetic efforts directed at monolabeled deoxyribose
derivatives has prompted consideration of a second generation strategy for
the population labeling of an oligonucleotide, in which incorporation of
multiple 13C labels into deoxyribose precursors would enhance both effi-
ciency of our synthetic scheme and the degree to which 13C label is in-
corporated into synthetic oligonucleotides. Toward this end, we have
examined the preparation of 1,3,5-13C3- and 2,4-13C2-labeled deoxyribose
systems, reasoning that incorporation of an equimolar mixture of these in-
termediates into synthetic oligonucleotides would effectively label each of the
carbohydrate backbone carbons of the resulting DNA polymer at an overall
enrichment of ꢀ 50-fold over natural abundance. Besides being an appealing
alternative for nucleotide structural determination3, the 1,3,5-13C3- and
2,4-13C2-labeled deoxyribose systems maximize the contribution of one-bond
13C-1H dipolar effects to NMR relaxation properties. These isotopomers
remove one- and three-bond 13C-13C coupling effects that complicate the
interpretation of relaxation properties; only natural abundance 13C-13C ad-
jacencies remain. The labeling scheme also provides obvious advantages in
sensitivity and reduction of spectral crowding, as well as presenting inter-
esting possibilities for spectral editing and efficient measurement of residual
dipolar couplings in oriented systems4. Furthermore, recent advances in solid
phase oligonucleotide synthesis, indicated that incorporation of precious
labeled phosphoramidites into oligonucleotides could be achieved much
more efficiently using only 1.75 equivalents5 of labeled reagent, as opposed to
the 10-fold excess normally required6. In contrast to the work of Serianni and
Bondo7, and Agrofoglio et al.8, whose methodology can also be used to
create 13C-enriched 2-deoxy-D-ribose, our method does not require the
synthesis of D-ribose followed by deoxygenation at C2 to create 2-deoxy-D-
ribose.
Our previously reported2 route to the isotopomeric series of 13C1-la-
beled deoxyribose derivatives, while designed to maximize economy of syn-
thetic effort, is intrinsically limited by the necessity of preparing five unique
isotopomers of deoxyribose. An additional liability of our initial approach
was the undesired introduction of the minor enantiomer of each isotopomer
as the consequence of an early asymmetric transformation that proceeds with
high, but not exclusive, stereoselectivity. To address these concerns, we have
considered alternative 13C-labeled precursors to population-labeled oligo-
nucleotides that can be accessed with increased efficiency and an improved
control of absolute stereochemistry. Attractive in both regards is the labeling
scheme depicted in Fig. 1, in which an equimolar mixture of 1,3,5-13C3 and
2,4-13C2-deoxyribonolactones 1,3,5-13C3-2 and 2,4-13C2-2 would yield the

2-DEOXYRIBONOLACTONES
1963
Figure 1. Retrosynthesis of 50% mixture of 1,3,5-13C3- and 2,4-13C2-deoxyribonolactones
(top center). The labels originate from 2-13C-bromoacetic acid (bottom center) and K13CN.
population-labeled deoxyribonolactones pl-1. Oligonucleotides derived from
pl-1 would be expected to exhibit an impressive 13C sensitivity enhancement
over unlabeled oligomers and over the previously reported monolabeled
systems2. Herein we describe the short and stereocontrolled routes to deox-
yribonolactones 1,3,5-13C3-2 and 2,4-13C2-2, as well as preliminary spectro-
scopic observations on these compounds and the population-labeled
mixtures obtained there from.
RESULTS AND DISCUSSION
Our integrated synthetic plan for preparing multiple 13C-labeled deox-
yribose derivatives, based on our previously reported conversion of differ-
entiated 2,3-epoxy butanediols 3 to the corresponding lactones via a modified
Payne homologation methodology, is shown in Fig. 1. The substrates for
Payne homologation, epoxy alcohols 1,3-13C2-3 and 2,4-13C2-3, were envi-
sioned deriving from a common starting material, the readily available 2-13C-
bromoacetic acid. For our preparation of 1,3,5-13C3-2, we anticipated in-
troducing the final 13C label at C1 from 13C-labeled cyanide ion. In-
corporation of the bromobenzyl ether system for protection of the C4 alcohol
was expected to facilitate removal of minor enantiomeric impurities by
crystallization, providing optically pure final products9.
Our synthesis of 1,3,5-13C3-2 is shown in Scheme 1. O-Alkylation of
2-13C-bromoacetic acid with 4-bromobenzyl alcohol followed by treatment of
the crude product with diazomethane yielded methyl ester 4. Reduction to
aldehyde 5, was achieved with DIBAL at ꢁ 78ꢂC, trace amounts ( < 10%) of
the over-reduced alcohol were separated by from 5 by chromatography.

1964
HATALA, KALLMERTEN, AND BORER
Scheme 1. Reagents: (a) KH, BrBnOH, THF, Á; (b) CH2N2, Et2O, 0ꢂC; (c) DIBAL, THF,
ꢁ 78ꢂC; (d) NaH, DME, 0ꢂC; (e) DIBAL, THF, 0ꢂC; (f) TBHP, Ti(OiPr)4, D-(-)-DIPT,
DCM, ꢁ 20ꢂC; (g) K13CN, KI, EtOH-H2O, Á, then HCl, H2O.
Homologation of 5 by Wadsworth-Emmons-Horner addition with labeled
phosphonate 610 furnished the unsaturated ester (not shown), which was di-
rectly reduced with DIBAL to allylic alcohol 2,4-13C2-7. Sharpless asymmetric
epoxidation11 of 2,4-13C2-7 gave epoxide 2,4-13C2-3 as a single enantiomer12
after one recrystallization. Payne rearrangement of epoxide 2,4-13C2-3 and
homologation13 with K13CN, produced a hydroxy nitrile which after hydro-
lysis and lactonization with aqueous HCl, afforded 1,3,5-13C3-2.
For our synthesis of 2,4-13C2-2, we proposed to exploit the latent
symmetry of the differentiated butendiol 7, as depicted in Scheme 2. Pro-
tection of 2-13C-bromoacetic acid as the 4-methoxybenzyl ether and ester-
ification with diazomethane afforded methyl ester 8. Reduction to the
corresponding aldehyde 9, addition of phosphonate 6, and reduction with
DIBAL yielded the 4-methoxybenzyl protected butenediol derivative 10. At
this juncture, the diol system of 10 was inverted by protection of the free
Scheme 2. Reagents: (a) KH, PMBOH, THF, Á; (b) CH2N2, Et2O, 0ꢂC; (c) DIBAL, THF,
ꢁ 78ꢂC; (d) NaH, DME, 6, 0ꢂC; (e) DIBAL, THF, 0ꢂC; (f) NaH, THF, BrBnBr, 0ꢂC; (g)
DDQ, 9:1 DCM:H2O, 0ꢂC; (h) TBHP, Ti(OiPr)4, D-(-)-DIPT, DCM, ꢁ 20ꢂC; (i) KCN, KI,
EtOH-H2O, Á, then HCl, H2O.

2-DEOXYRIBONOLACTONES
1965
alcohol as the 4-bromobenzyl ether, and selective cleavage of the 4-meth-
oxybenzyl residue14 gave allylic alcohol 1,3-13C2-7. Conversion to 2,4-13C2-2
was then accomplished as described for Scheme 115.
To complete our labeling strategy, equimolar amounts of 1,3,5-13C3-2
and 2,4-13C2-2 were combined to produces the population labeled mixture
50% pl-1. The HSQC spectrum of pl-1 was acquired and compared with the
HSQC spectrum for 2,4-13C2-2 (Fig. 2). All 13C-1H correlations appear in the
spectrum of pl-1 (panel a), but only the correlations for C2-H2,H20 and C4-
H4 appear in panel b.
Since we are primarily concerned with the interpretation of relaxation
properties, we determined the 2J coupling constants. Multiple-bond pathways
through the ring oxygen may also contribute to these small coupling constant
values. The values are shown in Table 1. We also measure a mutiple-bond
13C-13C coupling between C1 and C5. Selected spectra are shown (Fig. 3). The
larger two-bond and smaller multiple-bond couplings are clearly present for
2
C1 (Fig. 3a). For C3, both JC3-C5 and 2JC3-C1 couplings are visible (Fig. 3b,
left), but for C5, the 2JC5-C3 and the 3J=4JC5-C1 are closer in magnitude so only
a triplet appears (Fig. 3b, right). Of course C2 is split by 2JC2-C4 as shown (Fig.
2c); the identical coupling constant value was observed at C4 (not shown).
CONCLUSION
We have successfully prepared a new class of population-labeled
deoxyribonolactones with ꢀ 50-fold increase in 13C sensitivity over natural
abundance. The regioselectively labeled lactones are prepared en-
antiospecifically, and display 13C-13C couplings of no greater than 1.6Hz.
The individual deoxyribonolactones are highly stable intermediates and can
be stored for extended periods at ꢁ 20ꢂC, prior to combination and con-
version to nucleoside phosphoramidites for use in DNA synthesis. The
overall synthetic scheme is sufficiently flexible to allow preparation of all 13C-
isotopomers of DNA sugars in high yield. In our previous paper, the
syntheses of five x-13C1 and four 1,x-13C2-deoxyribonolactone17 isotopomers
is demonstrated. This paper describes the 1,3,5-13C3 and 2,4-13C2-lactones;
simple substitution of unlabeled cyanide affords the 3,5-13C2-lactone. This
accounts for 12 of the 32 isotopomers of 2-deoxy-D-ribose. Further work in
progress demonstrates procedures for the other isotopomers as well as at-
tractive population-labeled mixtures.
EXPERIMENTAL SECTION
General: IR spectra were recorded on a Perkin Elmer Paragon 1000 FT
spectrometer, with sodium chloride plates, and are reported in wavenumbers
1
(cmꢁ 1). H- and 13C NMR were taken on a Bruker Avance 300 unless

1966
HATALA, KALLMERTEN, AND BORER
Figure 2. HSQC spectra of 50% pl-1 (panel a), and 2,4-13C2-2 (panel b).

2-DEOXYRIBONOLACTONES
Table 1. 13C-13C Coupling Constants (in Hz)16
1967
2J
3J=4J
C1-C3
C3-C5
C2-C4
C1-C5
1.6
0.9
0.8
–
–
–
–
0.5
otherwise noted. Proton chemical shifts are reported in d, using the residual
CHCl3, as internal reference (7.26ppm), unless otherwise noted. J values are
given in Hz. Carbon chemical shifts are reported in d, using CDCl3, as an
1
internal reference (77.0ppm), unless otherwise noted. H and 13C NMR
spectra were typically acquired in the same number of scans. Optical rota-
tions were measured on either a Jasco DIP-1000 or a Perkin Elmer 241
spectrometer. Enantiomeric excess was determined by either Mosher ester
19
derivatization (ME)18, or by chiral shift analysis (CSA) with (þ)-Eu(hfc)3
.
THF and DME were distilled from sodium benzophenone ketyl under a
nitrogen atmosphere. Dichloromethane, benzene and pyridine were distilled
from calcium hydride before use. Hexanes, ethyl acetate, ether, and anhy-
drous ether were used from the supplier without further purification. Silica
gel (230–400 mesh) was used for flash column chromatography. TLC analysis
was performed on Whatman K6F silica gel 60 plates and were stained with
the following: anisaldehyde (method A), phosphomolybdic acid (PMA)
(method B), KMnO4 (method C), 2,4-DNP (method D), and UV light.
Reactions were performed in flame or oven dried glassware under a nitrogen
or argon atmosphere where appropriate. Other reagents were used from
suppliers without purification unless otherwise indicated.
HSQC spectra were acquired on a Bruker Avance 500 spectrometer,
using the pulse program of Palmer et al.20 HSQC spectra were collected with
Figure 3. 13C-13C Coupling for (a) C1, (b) C3 (left), and C5 (right), and (c) C2. Each panel is
0.35ppm.

1968
HATALA, KALLMERTEN, AND BORER
1 scan per increment, into 20486512 points with no sample spinning and no
zero-filling. These gradient selected acquisitions typically required > 15min.
The sweep width was 3255Hz in F2 and 12500Hz in F1. A squared sine
window function was applied in F2 and F1.
Data for coupling constants was acquired on a Bruker Avance 300 with
a direct detection probe. The sweep width was 450Hz, and no window
function was applied. The peaks were fitted using the NMR1 software
package (Tripos Assoc.) and coupling constants calculated assuming first-
order coupling.
[2-13C]-(4-Bromo-benzyloxy)-acetic acid methyl ester (4).
T
o
a
suspension of KH (722mg, 18mmol), washed with pentane, in 100mL of
THF at 0ꢂC was added 2-13C-bromoacetic acid (1g, 0.71mmol), and then
4-bromobenzyl alcohol (1.46g, 0.86mmol) both in 15mL of THF. The
reaction mixture was allowed to warm to room temperature and stirred
until the effervescence ceased. The solution was then heated to reflux
overnight. After cooling to ambient temperature the reaction mixture was
quenched by pouring into a stirring mixture of ice=NH4Cl (sat.)=ether
30mL each. The quenched reaction mixture was then transferred to a
separatory funnel and the organic layer was washed with NaHCO3 (sat.).
The organic layer was then discarded and the aqueous layer acidified with
concd. HCl until acidic. The aqueous layer was then extracted with three
50mL portions of ether, which were dried and concentrated to a white
solid. The solid was redissolved in ether, and diazomethane was added
to the ether solution at 0ꢂC until a yellow color persisted. Excess
diazomethane was quenched with MgSO4, and then filtered and
concentrated to yield a slightly yellow oil (1.73g, 95% over 2 steps).
1
Rf ¼ 0.64, 1:1 hexanes:EtOAc, method D; IR (neat): 3000.3, 1759.6; H
NMR: 3.69 (s, 3H), 4.05 (d, J ¼ 143.8, 2H), 4,51 (d, J ¼ 4.4, 2H), 7.18 (m,
2H), 7.41 (m, 2H); 13C NMR: 67.10.
[2-13C]-(E)-(4-Methoxy-benzyloxy)-acetic acid methyl ester (8). The
procedure for 4 was followed except 4-methoxybenzyl alcohol was
substituted for 4-bromobenzyl alcohol. The procedure yielded a slightly
yellow solid (1.33g, 90% over 2 steps). Rf ¼ 0.60, 1:1 hexanes:EtOAc,
1
method D; IR (neat): 3005.4, 1760.3; H NMR: 3.69 (s, 3H), 4.05 (d,
J ¼ 143.8, 2H), 4.51 (d, J ¼ 4.4, 2H), 7.18 (m, 2H), 7.41 (m, 2H); 13C
NMR: 67.10.
[2,4-13C2]-(E)-4-(4-Bromo-benzyloxy)-but-2-enoic
acid
methyl
ester. Methyl ester 4 (1.73g, 0.66mmol) was dissolved in 25mL of THF
and added to a round bottomed flask. The resulting homogenous solution
was cooled to ꢁ 78ꢂC and DIBAL (1.2eq, 8mL, 1M in toluene) was
added dropwise to the solution The reaction was monitored by TLC, and

2-DEOXYRIBONOLACTONES
1969
when the starting material had been consumed the resulting mixture was
quenched with MeOH. The quenched solution was allowed to warm to
ambient temperature, and was further diluted with ether and Rochelle salt.
After stirring for 2h the diluted solution was transferred to a separatory
funnel and extracted with two 100mL portions of ether, which were dried
over MgSO4, and conc. to yield a yellow oil. The aldehyde (5) was flashed
in 1:1 hexane:EtOAc. The aldehyde should be used immediately in the next
1
step. Rf ¼ 0.27, 1:1 hexane:EtOAc, method D; H NMR: 4.12 (d, J ¼ 145.4,
2H), 4.58 (d, J ¼ 6.9, 2H), 7.23 (d, J ¼ 8.3, 2H), 7.50 (d, J ¼ 8.5, 2H), 9.72
(d, J ¼ 29.7, 1H); 13C NMR: 75.4.
To a suspension of NaH (155mg, 0.65mmol) (washed with pentane) in
25mL DME was added [2-13C]-(diethoxy-phosphoryl)-acetic acid methyl
ester (6) (1.37g, 0.65mmol). The resulting reaction mixture was equilibrated
for 30min. After equilibration, the solution was cooled to ꢁ 78ꢂC and the
aldehyde (1.26g, 0.54mmol) was added dropwise in 5mL DME. The reaction
mixture was stirred for 30min and then quenched by pouring into a stirring
solution of ice=NH4Cl (sat)=ether 10mL each. Separation of the layers and
extraction of the organic layer, followed by drying over MgSO4 and conc
yielded a clear oil (1.12g, 59% over 2 steps). Rf ¼ 0.57, 1:1 hexanes: EtOAc,
1
method D; IR (neat): 1719.4; H NMR: 3.71 (s, 3H), 4.13 (dm, J ¼ 141.61,
2H), 4.46 (d, J ¼ 4.12, 2H), 6.09 (dm, J ¼ 165.21, 1H), 6.94 (m, 1H), 7.18
(d, J ¼ 8.23, 2H), 7.44 (d, J ¼ 8.23, 2H); 13C NMR: 68.49, 120.79.
[2,4-13C2]-(E)-4-(4-Methoxy-benzyloxy)-but-2-enoic acid methyl ester.
The above procedure, applied to 8, yielded a yellow oil. Aldehyde:
1
Rf ¼ 0.24, 1:1 hexane:EtOAc, method D; IR (neat): 1723; H NMR: 3.81
(s, 3H), 4.06 (dd, J ¼ 0.5, 141.3, 2H), 4.56 (d, J ¼ 4.39, 2H), 6.89 (d,
J ¼ 8.8, 2H), 7.29 (d, J ¼ 8.8, 2H), 9.69 (d, J ¼ 25.8, 1H); 13C NMR: 75.0.
The above procedure, applied to 9, yielded a yellow oil (975mg, 65% over
2 steps). Ester: Rf ¼ 0.61, 1:1 hexanes:EtOAc, method D; IR (neat): 1720.2;
1H NMR: 3.74 (s, 3H), 3.81 (s, 3H), 4.14 (dm, J ¼ 142.43, 2H), 4.49 (d,
J ¼ 4.39, 2H), 6.11 (dm, J ¼ 163.57, 1H), 6.97 (m, 1H), 6.88 (m, 2H), 7.27
(m, 2H); 13C NMR: 68.25, 120.86.
[2,4-13C2]-(E)-4-(4-Bromo-benzyloxy)-but-2-en-1-ol (2,4-13C2-7). The
unsaturated ester (1.12g, 0.39mmol) was dissolved in THF and cooled to
0ꢂC in ice. DIBAL (2.5eq, 13.5mL, 1M in toluene) was added to the
stirring solution and the resulting mixture was allowed to warm to ambient
temperature. After stirring for 2h the mixture was again cooled to 0ꢂC
and was quenched with MeOH and then diluted with ether and Rochelle
salt and stirred overnight. Extraction of the quenched reaction mixture
followed by drying over MgSO4, and conc to yield a clear oil (900mg,
89%). Rf ¼ 0.35, 1:1 hexanes:EtOAc, method A; IR (neat): 3388.4, 2853.2;
1H NMR: 1.77 (s, 1H), 4.02 (dt, J ¼ 5.49, 141.34, 2H), 4.16 (m, 2H), 4.46

1970
HATALA, KALLMERTEN, AND BORER
(d, J ¼ 3.57, 2H), 5.83 (m, 1H), 5.90 (dm, J ¼ 151.49, 1H), 7.21 (d, J ¼ 8.51,
2H), 7.47 (d, J ¼ 8.23, 2H); 13C NMR: 70.14, 132.38.
[2,4-13C2]-(E)-4-(4-Methoxy-benzyloxy)-but-2-en-1-ol (10). The above
procedure, applied to the unsaturated ester from 9, yielded a clear oil
(800mg, 93%). Rf ¼ 0.29, 1:1 hexanes:EtOAc, method A; IR (neat): 3388.8,
1
2838.2; H NMR: 1.63 (bs, 1H), 3.80 (s, 3H), 4.00 (dm, J ¼ 139.96, 2H),
4.15 (m, 2H), 4.45 (d, J ¼ 4.12, 2H), 5.83 (m, 1H), 5.89 (dm, J ¼ 152.31,
1H), 6.88 (m, 2H), 7.26 (m, 2H); 13C NMR: 69.8, 132.1.
[1,3-13C2]-(E)-1-(4-Bromo-benzyloxy)-4-(4-Methoxy-benzyloxy)-but-2-
ene (11). To a round bottom flask was added NaH (137mg, 0.57mmol) and
5mL of THF. The resulting solution was cooled to 0ꢂC in ice. Compound 10
was then added followed by bromobenzyl bromide (1.40g, 0.57mmol) in 2
portions. The reaction was then allowed to warm to room temperature and
monitored by TLC. After the starting material was consumed the reaction
was quenched with sat. NH4Cl. Typical workup provided an oil (1.25g,
1
87%). Rf ¼ 0.84, 1:1 hexane:EtOAc; IR (neat): 2854.0; H NMR: 3.80 (s,
3H), 4.01 (dt, J ¼ 4.7, 141.3, 2H), 4.03 (t, J ¼ 4.9, 2H), 4.45 (m, 2H), 5.85
(dm, J ¼ 152.3, 1H), 5.86 (m, 1H), 6.88 (d, J ¼ 8.5, 2H), 7.24 (m, 4H), 7.46
(d, J ¼ 8.5, 2H); 13C NMR: 69.8, 129.1.
[1,3-13C2]-(E)-4-(4-Bromo-benzyloxy)-but-2-en-1-ol (1,3-13C2-7). 11 was
dissolved in 9:1 DCM:H2O, and cooled to 0ꢂC in ice. DDQ was then added
all at once and the reaction was stirred for 1h. Extraction, drying, and conc
yielded an oil (820mg, 96%). IR (neat): 3388.4, 2853.2; 1H NMR: 1.48 (br s,
1H), 4.03 (t, J ¼ 4.9, 2H), 4.16 (dt, J ¼ 5.5, 142.2, 2H), 4.47 (s, 2H), 5.84 (dm,
J ¼ 153.4, 1H), 5.91 (m, 1H), 7.21 (d, J ¼ 8.0, 2H), 7.47 (d, J ¼ 8.2, 2H);
13C NMR: 63.0, 128.3.
[2,4-13C2]-(2R,3R)-[3-(4-Bromo-benzyloxymethyl)-oxiranyl]-methanol
(2,4-13C2-3). To a round bottom flask was added powdered, activated 4A
molecular sieves, and a stir bar. The round bottom flask was then flame
dried and allowed to cool to ambient temperature under nitrogen.
Methylene chloride, D-(-)-diisopropyl tartrate, and Ti(OiPr)4 were added
sequentially, and the resulting heterogeneous solution was cooled to
ꢁ25ꢂC (CO2 (s), CCl4) and stirred for 30min. TBHP was then added at
ꢁ25ꢂC, and the solution was aged for 30min. Meanwhile, the allylic
alcohol 2,4-13C2-7 was diluted in DCM and stirred over 4A molecular
sieves while the catalyst was aging. After the aging period the allylic
alcohol was added to the catalyst and the reaction mixture was stirred
at ꢁ25ꢂC for 1h before being placed in a ꢁ20ꢂC freezer overnight.
The reaction mixture was quenched by addition of dimethyl sulfide at
ꢁ20ꢂC and allowing the solution to warm to ambient temperature over

2-DEOXYRIBONOLACTONES
1971
2h. The quenched mixture was filtered through a frit and concentrated to
yield a yellow crude product that was purified by flash chromatography to
afford as a white solid. Recrystallization was conducted as follows: the
solid obtained after flash chromatography was suspended in pentane (1–
2mL), and then ether was added until the solution became
homogeneous at room temperature. The solution was then placed in a
ꢁ25ꢂC freezer overnight to allow crystal formation. White needles
(826mg, 86%). ee ¼ 100% (ME); Rf ¼ 0.39, 2:1 hexane:EtOAc, method
1
A; IR (thin film): 3356.5; H NMR: 1.77 (br s, 1H), 3.09 (d, J ¼ 173.7,
1H), 3.24 (m, 1H), 3.71 (m, 2H), 3.78 (dm, J ¼ 141.9, 2H), 3.94 (d,
J ¼ 12.6, 1H), 4.52 (ABq, J ¼ 13.7, 2H), 7.21 (d, J ¼ 8.2, 2H), 7.47 (d,
J ¼ 8.5, 2H); 13C NMR: 55.5, 69.7.
[1,3-13C2]-(2R,3R)-[3-(4-Bromo-benzyloxymethyl)-oxiranyl]-methanol
(1,3-13C2-3). The above procedure applied to 1,3-13C2-7 yielded white
1
needles (704mg, 80%). ee ¼ 100% (ME); IR (thin film): 4305; H NMR:
2.12 (br s, 1H), 3.08 (m, 1H), 3.20 (d, J ¼ 158.1, 1H), 3.63 (dd, J ¼ 13.2,
142.7, 2H), 3.77 (d, J ¼ 10.7, 1H), 4.16 (d, J ¼ 12.9, 1H), 4.51 (ABq,
J ¼ 11.5, 2H), 7.20 (d, J ¼ 7.4, 2H), 7.46 (d, J ¼ 7.4, 2H); 13C NMR: 54.1,
61.0.
[1,3,5-13C3]-(4S,5R)-5-(4-Bromo-benzyloxymethyl)-4-hydroxy-dihydro-
furan-2-one (1,3,5-13C3-2). To a solution of epoxide 2,4-13C2-3 in 120mL of
2:1 EtOH:H2O, was added K13CN and KI. The reaction mixture was heated
at reflux for 48hr, cooled to ambient temperature and carefully acidified to
pH 2 with 10% HCl. The resulting mixture was warmed to 60ꢂC and
stirred for 16h, at which time the reaction mixture was cooled and
transferred to a separatory funnel and the aqueous layer was extracted
with three 50mL portions of Et2O. The combined ether extracts were dried
over MgSO4, filtered, and concentrated. The crude product was purified by
flash chromatography (2:1 hexanes:EtOAc) to give lactone 1,3,5-13C3-2 as
a slightly yellow solid (593mg, 65%). Rf ¼ 0.31, 2:1 hexanes:EtOAc,
1
method A; IR (thin film): 3387, 1780; H NMR: 2.70 (br s, 1H), 2.45 (dm,
J ¼ 2.7, 18.0, 1H), 2.91 (dt, J ¼ 5.8, 18.3, 1H), 3.66 (dm, J ¼ 144.0, 2H),
4.46 (m, 3H), 4.51 (dm, J ¼ 153.5, 1H), 7.14 (d, J ¼ 8.2, 2H), 7.47 (d,
J ¼ 8.5, 2H); 13C NMR: 69.5, 69.6, 175.9.
[2,4-13C2]-(4S,5R)-5-(4-Bromo-benzyloxymethyl)-4-hydroxy-dihydro-
furan-2-one (2,4-13C2-2). The above procedure applied to 1,3-13C2-7 yielded
a yellow solid (479mg, 60%). IR (thin film): 3365, 1772; 1H NMR: 2.71 (br s,
1H), 2.45 (ddd, J ¼ 1.8, 18.3, 136.8, 1H), 2.92 (ddd, J ¼ 6.7, 18.3, 133.7, 1H),
3.67 (m, 2H), 4.46 (ABq, J ¼ 11.0, 2H), 4.48 (d, J ¼ 150.5, 1H), 4.53 (m, 1H),
7.14 (d, J ¼ 8.2, 2H), 7.47 (d, J ¼ 8.2, 2H); 13C NMR: 38.4, 86.2.

1972
HATALA, KALLMERTEN, AND BORER
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Received April 10, 2001
Accepted September 26, 2001