An Efficient Preparation of 2-C-Methyl-D-Erythritol 4-Phosphoric Acid and Its Derivatives

Full text of DOI:10.1021/jo9905118

J . Org. Chem. 2000, 65, 587-592
587
We decided to synthesize 2-C-methyl-D-erythritol 4-phos-
phate to study its potential involvement in the deoxyxyl-
ulose pathway of terpenoid biosynthesis. The synthetic
strategy was designed to permit the introduction of stable
or radioactive isotopes in different steps, thus leading to
a set of labeled compounds, necessary for mechanistical
studies of the alternative terpenoid pathway.
An Efficien t P r ep a r a tion of
2-C-Meth yl-D-Er yth r itol 4-P h osp h or ic Acid
a n d Its Der iva tives
Klaus Kis,† J uraithip Wungsintaweekul,‡
Wolfgang Eisenreich,† Meinhart H. Zenk,‡ and
Adelbert Bacher*,†
Institut fu¨r Organische Chemie und Biochemie, Technische
Universita¨t Mu¨nchen, Lichtenbergstr. 4, D-85747 Garching,
Federal Republic of Germany, and Institut fu¨r
Pharmazeutische Biologie, Ludwig-Maximilians-Universita¨t
Mu¨nchen, Karlstr. 29, D-80333 Mu¨nchen, Germany
Resu lts a n d Discu ssion
Derivatives of 2-C-methyl-D-erythritol and racemic 2-C-
methyl-threitol were prepared in 1980 by Anthonsen et
al.15 In 1982, Yoshimura reported the synthesis of deriva-
tives of 2-C-methyl-erythritol and 2-C-methyl-erythrose.16
The reaction sequence was hampered by the formation
of numerous byproducts and low yields. Retrosynthetic
analysis suggested 2-C-methyl-D-erythrono-1,4-lactone
(12) as starting material for the preparation of the
putative terpene precursor, 2-C-methyl-D-erythritol 4-phos-
phate. De Pascual Teresa17 and Ford18 had obtained 12
as a natural product from the plants Astragalus lusi-
tanicus Lam. and Cicer ariatinum. The lactone was
thought to be a plant growth regulator involved in
feedback inhibition in the biosynthesis of valine. Mu-
kaiyama et al. and Kobayashi have reported the synthe-
sis of 12 and 2-C-methyl-D-threono-1,4-lactone (13), the
latter compound with an enantiomeric excess of >98%.19,20
Our initial attempt to generate the carboxylic acid 11
directly from 3,4-dihydroxy-2-butanone by cyanohydrin
formation failed because the starting material formed
butane-2,3-dione by dehydration under the reaction
conditions. We decided to synthesize 12 from 1,2:5,6-di-
O-isopropylidene-D-mannitol (6) (Scheme 2). This ap-
proach facilitates the introduction of stable or radioactive
isotopes.
Cleavage of 6 with lead tetraacetate followed by
subsequent treatment of the resulting isopropylidene
glyceraldehyde (7) with methylmagnesium iodide and
oxidation afforded (3R)-3,4-O-isopropylidene-2-butanone
(9).21 Reaction of 9 with trimethylcyanosilane under
catalysis with KCN and 18-crown-6 quantitatively af-
forded (2R,3RS)-1,2-O-isopropylidene-3-O-trimethylsilyl-
1,2,3-trihydroxy-3-cyano-butane (10). The ratio of the
diastereomeric products 2R,3R and 2R,3S was 3:1, as
determined by NOE experiments of isopropylidene de-
rivative 14. Hydrolysis of the diastereomeric mixture
with 25% hydrochloric acid afforded a mixture of the
erythronolactone 12, threonolactone 13, and the corre-
sponding open chain carboxylic acids 11. Small amounts
of this reaction mixture could be purified by column
Received March 23, 1999
In tr od u ction
Isopentenyl pyrophosphate (IPP) and dimethylallyl
pyrophosphate (DMAPP) are the key intermediates in
terpenoid biosynthesis. Classical studies by Bloch, Corn-
forth, Lynen, and their co-workers have established that
IPP and DMAPP can be biosynthesized from acetyl-CoA
via mevalonate.1-4 More recently, an alternative pathway
was shown to be operative in certain bacteria and in plant
chloroplasts.5-8 The initial step of the novel pathway
involves the thiamine pyrophosphate dependent conden-
sation of pyruvate (1) with glyceraldehyde 3-phosphate
(2) affording 1-deoxy-D-xylulose 5-phosphate (3). The
availability of compounds such as 3 is of great importance
for the elucidation of the later steps of this novel
pathway. Recently, Blagg and Poulter could improve the
synthesis of 3 from 5% to 58% in a reaction sequence that
allows the introduction of carbon or hydrogen isotopes.9
Most recently, Thiel and Adam described the introduction
of 2H in position C-5 of 3.10 Recent evidence indicates that
deoxyxylulose 5-phosphate can be converted to 2-C-
methyl-D-erythritol 4-phosphate (5) by an enzyme from
Escherichia coli that catalyzes a two-step reaction involv-
ing an intramolecular rearrangement via aldehyde 4
followed by reduction (Scheme 1).11,12 This reduction step
was shown to proceed stereospecifically in Liriodendron
tulipifera and Synechocystis sp. PCC6803.13,14
* Tel.+49-89-289-13360.Fax: +49-89-289-13363.E-mail: adelbert.bacher@
ch.tum.de.
† Technische Universita¨t Mu¨nchen.
‡ Ludwig-Maximilians-Universita¨t Mu¨nchen.
(1) Bloch, K. Steroids 1992, 57, 378-382.
(2) Qureshi, N.; Porter, J . W. In Biosynthesis of Isoprenoid Com-
pounds; Porter, J . W., Spurgeon, S. L., Eds.; J ohn Wiley: New York,
1981; Vol. 1, pp 47-94.
(3) Banthorpe, D. V.; Charlwood, B. V.; Francis, M. J . O. Chem. Rev.
1972, 72, 115-155.
(4) Bach, T. J . Lipids 1995, 30, 191-202.
(5) Flesch, G.; Rohmer, M. Eur. J . Biochem. 1988, 175, 405-411.
(6) Rohmer, M.; Knani, M.; Simonin, P.; Sulter, B.; Sahm, H.
Biochem. J . 1993, 295, 517-524.
(14) Proteau, P. J .; Woo, Y.-H.; Williamson, R. T.; Phaosiri, C. Org.
Lett. 1999, 1, 921-923.
(15) Anthonsen, T.; Hagen, S.; Sallam, M. A. E. Phytochemistry
1980, 19, 2375-2377.
(16) Yoshimura, J .; Hara, K.; Yamaura, M.; Mikamin, K.; Hash-
imoto, H. Bull. Chem. Soc. J pn. 1982, 55, 933-937.
(17) De Pascual Teresa, J .; Herna´ndesz Aubanell, J . C.; San Feli-
ciano, A.; Migel del Corral, J . M. Tetrahedron Lett. 1980, 21, 1359-
1360.
(7) Lichtenthaler, H. K.; Schwender, J .; Disch, A.; Rohmer, H.
Biochem. J . 1996, 316, 73-80.
(8) Seto, H.; Watanabe, H.; Furihata, K. Tetrahedron Lett. 1996,
37, 7979-7982.
(9) Blagg, B. S.; Poulter, C. D. J . Org. Chem. 1975, 40, 1508-1511.
(10) Thiel, R.; Adam, K. P. Tetrahedron Lett. 1999, 40, 5307-5308.
(11) Takahashi, S.; Kuzuyama, T.; Watanabe, H.; Seto, H. Proc. Natl.
Acad. Sci. U.S.A. 1998, 95, 9879-9884.
(18) Ford, C. W. Phytochemistry 1981, 20, 2019-2020.
(19) Mukaiyama, T.; Hiina, I.; Izumi, J .; Kobayashi, S. Heterocycles
1996, 35, 719-724.
(12) Kuzuyama, T.; Takahashi, S.; Watanabe, H.; Seto, H. Tetra-
hedron Lett. 1998, 39, 4509-4512.
(13) Arigoni, D.; Giner, J .-L.; Sagner, S.; Wungsintaweekul, J .; Zenk,
M. H.; Kis, K.; Bacher, A.; Eisenreich, W. Chem. Commun. 1999, 1127-
1128.
(20) Kobayashi, S.; Horibe, H.; Saito, Y. Tetrahedron 1994, 50,
9629-9642.
(21) Kis, K.; Volk, R.; Bacher, A. Biochemistry 1995, 34, 2883-2892.
10.1021/jo9905118 CCC: $19.00 © 2000 American Chemical Society
Published on Web 12/31/1999

588 J . Org. Chem., Vol. 65, No. 2, 2000
Sch em e 1. Biosyn th esis of IP P a n d DMAP P via th e Deoxyxylu lose P a th w a y
Notes
Sch em e 2a
a
Reagents and conditions: (a) Pb(OOCCH3)4, CH2Cl2, 0 °C (12 h); (b) (1) CH3MgI, Et2O, 0 f 25 °C (12 h), (2) H2O, NH4Cl; (c) RuO2,
NaIO4, K2CO3, CHCl3/H2O, 25 °C (2 d); (d) (CH3)3SiCN, KCN, 18-crown-6, CH2Cl2, 0 f 25 °C (30 min); (e) HCl (25%), H2O, EtOH, 40 f
80 °C (3 h); (f) HCOOH (60%), 80 °C (2 h); (g) CH3COCH3, ZnCl2, 25 °C (12 h); (h) (1) DIBAH (1.4 equiv), THF, -78 f 25 °C (2 h), (2) H2O,
-78 °C (1 h); (i) PhCH2ONH2, pyridine, CH2Cl2, 25 °C (12 h); (j) (1) (PhCH2O)3P, I2, CH2Cl2, -20 f 25 °C (30 min), (2) (PhCH2O)2POI,
pyridine, CH2Cl2, -20 °C (2 h); (k) (1) O3, pyridine, CH2Cl2, -78 °C (10 min), (2) CH3SCH3, -78 °C (1 h); (l) NaBH4, MeOH, 0 f 25 °C
(2 h); (m) (1) H2, Pd/C, MeOH (50%), 25 °C (12 h), (2) 70 °C (60 min).
chromatography on silica with EtOAc/2-propanol/H2O
(65:24:12; v/v/v) as solvent system. The compound eluted
first was identified as 13. The specific rotation [R]D -35.9°
was about two times larger than the value reported by
Mukaiyama et al. ([R]D -18°).19 The possibility of race-
mization of this compound was pointed out by De Pascual
Teresa et al.17 Elemental analysis, IR absorption at 1770
cm-1 (γ-lactone), and the impossibility to convert the

Notes
J . Org. Chem., Vol. 65, No. 2, 2000 589
Sch em e 3a
compound into a cyclic acetal with acetone established
the threono-1,4-lactone structure 13. The second (main)
fraction could be identified as the erythronolactone 12,
which could easily be transformed into a cyclic acetal with
acetone/ZnCl2. Compound 12 had a specific rotation of
[R]D -60.9°. This value is consistent with reported values
(-58.6° and -61.2°).17,20 The third fraction was very likely
a mixture of both diastereomeric open chain carboxylic
acids 11 as shown by NMR spectroscopy. The NMR
spectra of all three fractions agreed well with published
data.18,20 Lactonization of this reaction mixture was
performed to completeness with 60% formic acid at 80
°C. During this procedure the spot on TLC corresponding
to compound 11 completely disappeared. The mixture of
both lactones was then treated with acetone/ZnCl2. The
cyclic acetal 14 could be separated from unreacted 13 by
extraction with chloroform after dilution with water. The
unchanged 2-C-methyl-D-threono-1,4-lactone (13) re-
mained in the water phase and could be isolated and
purified. In addition to the specific rotation of 12 that
demonstrates the 2R,3R configuration of 2-C-methyl-D-
erythrono-1,4-lactone, further evidence for this configu-
ration was obtained from NOESY spectroscopy of its
isopropylidene derivative 14. The proton at 4.41 ppm
showed strong NOEs to two methyl groups located at 1.33
and 1.48 ppm. The proton at 4.24 ppm showed a strong
NOE to the methyl group at 1.48 ppm. Thus, the protons
at 1.48, 4.24, and 4.41 ppm are located on the same side
of the lactone ring plane. Finally, the proton at 4.34 ppm
did not show NOEs to the methyl groups at 1.33 and 1.48
ppm. In contrast, only a weak NOE to the methyl group
located at 1.37 ppm could be observed. Because the
configuration of carbon atom C-3 should remain R (as in
the starting material), during the synthesis the config-
a
Reagents and conditions: (a) CH3COOH (60%), 60 °C (1 h);
(b) (1) DIBAH (2.5 equiv), THF, -78 f 25 °C (2 h), (2) H2O, -78
°C (1 h); (c) CH3COOH (12%), 60 °C (3 h).
reported by Anthonsen ([R]578 +7.92) differ significantly.
This may be due to the different wavelength used.
Deprotection of 21 with 12% acetic acid at 60 °C afforded
2-C-methyl-D-erythritol (22) which had the same spec-
troscopic properties as an authentic sample. However,
[R]D of compound 22 was 50% smaller than reported.23,24
Ring opening of the protected hemiacetal 15 could
easily be achieved by oxime ether formation using O-
benzylhydroxylamine hydrochloride in pyridine. This
reaction proceeded smoothly at room temperature in high
yield, and the product could easily be extracted with
chloroform. Benzyloxime ether 16 was then phosphoryl-
ated using tribenzyl phosphite25 and iodine in dichlo-
romethane, affording 17 in 71% yield. Removal of the
benzyloxime ether group by boiling with benzaldehyde
under acid catalysis was not successful. Ozone cleavage
was considered as an alternative. Little is known about
ozonization of oximes. Erikson et al. reported that ozo-
nization of the carbon-nitrogen double bond may give
complex reaction mixtures, but carbonyl formation was
also observed.26 Recently, acyclic sugar aldehydes were
successfully prepared by ozonization of oximes by Weitz
and Bednarski.27 Although it was mentioned by Erikson
et al. that aldoximes may undergo further oxidation upon
treatment with ozone, we attempted the ozonization of
benzyloxime ether 17. Initially, a complex reaction
1
uration of C-2 should also be R. The H NMR signals at
1.48, 4.24, 4.34, and 4.41 ppm can now be assigned to
the C-2 methyl group, C-4 Hpro-R, C-4 Hpro-S, and C-3 HR,
respectively. The protons C-4 Hpro-S and C-3 HR have a
small coupling constant (≈ 0 Hz), suggesting a bond angle
near 90°, which is reasonable for such a rigid structure
in 14. The configuration of 12 and 14 is further cor-
roborated by the observed specific rotation of 14. This
compound showed a large specific rotation [R]D -82.5°
in acetone. Ishizu et al. reported a value of [R]D -40° for
14.22 Also here a partial racemization may have occured
during their preparation procedure. All these data sug-
gest that the configuration of 12 is 2R,3R, which is the
desired configuration of the final product 5.
Ring opening of 14 with methoxide in methanol af-
forded a complex product mixture. However, 14 could be
reduced with diisobutylaluminum hydride (DIBAH) yield-
ing the cyclic hemiacetals 15 in both anomeric forms (R/
â). The open chain aldehyde was not present in signifi-
cant amounts according to NMR spectra. Deprotection
of 15 with 60% acetic acid at 60 °C afforded 2-C-methyl-
D-erythrose (20) as cyclic acetals in 89% yield (Scheme
3). Again, no open chain aldehyde was present in this
anomeric mixture. Reduction of 14 with a 2.5-fold excess
of DIBAH resulted in quantitative reduction of the
lactone yielding 2,3-O-isopropylidene-2-C-methyl-D-eryth-
ritol (21). NMR data of this compound correspond to those
reported by Anthonsen.15 However, the specific rotation
of 21 determined by us ([R]D -26.0°) and the value
(23) Anthonsen, T.; Hagen, S.; Kazi, M.; Shah, S.; Tager, S. Acta
Chem. Scand. Ser. B 1976, 30, 91-93.
(24) Ostrovsky, D.; Shashkov, A.; Sviridov, A. Biochem. J . 1993, 295,
901-902.
(25) Gefflaut, T.; Lemaire, M.; Valentin, M.-L.; Bolte, J . J . Org.
Chem. 1997, 62, 5920-5922.
(26) Erikson, R. E.; Andrulis, P. J .; Collins, J . C.; Lungle, M. C.,
Mercer, G. D. J . Org. Chem. 1969, 34, 2961-2966.
(27) Weitz, D. J .; Bednarski, M. D. J . Org. Chem. 1989, 54, 4957-
4959.
(22) Ishizu, A.; Lindberg, B.; Theander, O. Acta Chem. Scand. 1967,
21, 424-432.

590 J . Org. Chem., Vol. 65, No. 2, 2000
Notes
was dissolved by the addition of saturated ammonium chloride
(50 mL). The organic layer was removed, and the water phase
was saturated with sodium chloride and extracted with chloro-
form (3 × 50 mL). The combined organic layers were dried with
magnesium sulfate, and the solvent was removed under reduced
pressure, affording 9.9 g (68 mmol, 84%) of (2R,3RS)-1,2-O-
isopropylidene-1,2,3-butanetriol as colorless oil. 1H NMR (360
MHz, CDCl3): δ (ppm) 0.96 (d, 3J ) 6.5 Hz), 1.07 (d, 3J ) 6.5
Hz), 1.24 (s), 1.25 (s), 1.29 (s), 1.33 (s), 3.41-3.47 (m), 3.67-
3
3
3.78 (m), 3.82-3.97 (m), 4.67 (d, J ) 4.6 Hz), 4.75 (d, J ) 5.2
Hz). 13C NMR (90 MHz, CDCl3): δ (ppm) 18.0, 19.8, 24.8, 26.1,
64.3, 65.9, 66.1, 66.9, 79.1, 79.3, 107.7, 107.7. Anal. Calcd for
(C7H14O3): C, 57.5; H, 9.90. Found: C, 57.2; H, 9.90.
(3R)-3,4-O-Isop r op ylid en e-3,4-d ih yd r oxy-2-bu ta n on e (9).
(2R,3RS)-1,2-O-Isopropylidene-1,2,3-butanetriol (8) (9.9 g, 68
mmol) was dissolved in 100 mL of chloroform. Water (100 mL),
30 g of potassium carbonate (0.22 mol), and 50 mg of ruthenium
dioxide hydrate was added. The suspension was stirred vigor-
ously at room temperature, and 29 g (0.14 mol) of sodium
periodate was added in small portions. The pH was repeatedly
adjusted to 8-8.5 by the addition of solid potassium carbonate.
After the addition of periodate was complete, the suspension was
stirred for 2 days at room temperature. Prior to workup, an
aliquot of the reaction mixture was checked by 1H NMR
spectroscopy. If starting material was still present, an additional
amount of periodate was added. When the oxidation was
complete, the suspension was filtered by suction, and the filtrate
was extracted with chloroform (4 × 50 mL). The combined
organic layers were dried with magnesium sulfate, and the
solvent was removed under reduced pressure affording 7.2 g (50
mmol, 74%) of (3R)-3,4-O-isopropylidene-3,4-dihydroxy-2-bu-
tanone as a colorless oil. 1H NMR (250 MHz, CDCl3): δ (ppm)
1.4 (s, 3H), 1.5 (s, 3H), 2.27 (s, 3H), 4.0 (dd, 2J ) 8.5 Hz, 3J )
5.5 Hz, 1H), 4.2 (dd, 2J ) 8.5 Hz, 3J ) 8.0, 1H), 4.41 (dd, 3J )
7.9 Hz, 3J ) 5.5 Hz, 1H). 13C NMR (62 MHz, CDCl3): δ (ppm)
25.3, 25.6, 26.3, 66.4, 80.4, 110.9. Anal. Calcd for (C7H12O3): C,
58.4; H, 8.33. Found: C, 57.9; H, 8.30. TLC Rf 0.71 (hexane/
EtOAc 1:4, v/v). [R]22 +49.0° (c 0.72, CH2Cl2) (lit. [R]20 +53.3°
F igu r e 1. 1H NMR spectrum of (top) 2-C-methyl-D-erythritol
4-phosphoric acid (5) and (bottom) 2-C-methyl-D-erythritol (22)
(500 MHz D2O, pH 1). The 2-C-methyl groups are not shown.
Assignments are given according to the notation of 5 in Scheme
1 (primes denote diastereotopic protons).
mixture was obtained, probably as a result of a pH
decrease of the solution. However, ozonization in the
presence of pyridine was successful, and the aldehyde
phosphate 18 could be isolated in 91% yield. This
aldehyde compound 18 is very unstable and polymerizes
even at -20 °C. The product 18 was then reduced with
an excess of sodium borohydride in methanol, affording
the 4-dibenzyl phosphate of 2,3-O-isopropylidene-2-C-
methyl-D-erythritol (19). Hydrogenation and subsequent
acidic hydrolysis of the isopropylidene group yielded 2-C-
methyl-D-erythritol 4-phosphoric acid (5) in 9% overall
D
D
(c 1.56, CHCl3),28 [R]20 +47.1° (c 1.87, CHCl3)29).
D
1
(2R,3RS)-1,2-O-Isop r op ylid en e-3-O-tr im eth ylsilyl-1,2,3-
tr ih yd r oxy-3-cya n o-bu ta n e (10). (3R)-3,4-O-Isopropylidene-
3,4-dihydroxy-2-butanone (9) (7.2 g, 50 mmol) was dissolved in
50 mL of dry dichloromethane. Catalytic amounts of potassium
cyanide (20 mg) and 18-crown-6 (20 mg) were added. Under
cooling with ice, 9.4 mL (70 mmol) of trimethylsilyl cyanide was
added within 20 min. The solvent and excess trimethylsilyl
cyanide were removed under reduced pressure. The orange
colored oily residue (12.0 g, 49.3 mmol, 99%) was a mixture of
the erythro and threo compound in a ratio of 3:1. The unstable
compound was used immediately without further purification.
1H NMR (360 MHz, CDCl3): δ (ppm) 0.17 and 0.18 (2s, 9H),
1.12, 1.29, 1.40, 1.43, 1.46 and 1.57 (6s, 9H), 3.85-3.90 (m, 1H),
3.97-4.10 (m, 2H). 13C NMR (90 MHz, CDCl3): erythro δ (ppm)
1.2, 24.0, 25.0, 26.0, 65.0, 80.4, 110.9; threo δ (ppm) -3.1, 25.2,
26.2, 26.4, 66.4, 80.8, 120.7. Anal. Calcd for (C11H21NO3Si): C,
54.3; H, 8.63; N, 5.76; Si, 11.6. Found: C, 53.9; H, 8.79; N, 5.51;
Si, 12.4.
yield after 14 steps (for H NMR, see Figure 1). Isotopic
labels can be introduced during the reaction steps 7 f
8, 9 f 10, 14 f 15, and 18 f 19, which would afford
3
labels (2H, H, 13C, or 14C) in the positions C2′ or C1 of 5.
Exp er im en ta l Section
Ma ter ia ls. Chemicals were obtained from Aldrich Chemicals
(Steinheim, Germany) and were used without further purifica-
tion. Solvents were dried prior to use. Potassium carbonate and
magnesium sulfate were dried under reduced pressure at 120
°C. Silica gel was activated by drying at 120 °C for 2 days. TLC
was performed on silica plates, and the compounds were
visualized by fluorescence quenching, 2,4-dinitrophenylhydra-
zine (2% in ethanol containing 13% H2SO4), or lead tetraacetate
(1% in toluene). All compounds gave only one single spot. NMR
spectra were recorded at room temperature.
(2R,3RS)-1,2-O-Isop r op ylid en e-1,2,3-bu ta n etr iol (8). 1,2:
5,6-Di-O-isopropylidene-D-mannitol (6) (14.0 g, 53.0 mmol) was
dissolved in 200 mL of dry chloroform. Anhydrous potassium
carbonate (50.5 g, 366 mmol) was added, and the suspension
was cooled to 0 °C. Lead tetraacetate (27.1 g, 61.1 mmol) was
added in small portions under vigorous stirring. The orange
suspension was allowed to stand at room temperature overnight.
Potassium carbonate was filtered off by suction, and the filter
cake was washed repeatedly with ether. The combined filtrate
and washings were dried with magnesium sulfate, and the
solvent was removed under reduced pressure. The oily residue
was quickly distilled (60 °C at 30 mbar), affording 10.5 g (80.7
mmol, 76%) isopropylidene glyceraldehyde 7. The product was
immediately dissolved in 35 mL of dry ether to avoid polymer-
ization. The solution was added to a cooled solution of methyl-
magnesium iodide prepared from 5.1 g (0.22 mol) of magnesium
and 13 mL (0.21 mol) of methyl iodide in 140 mL of ether. After
the aldehyde was added completely, the solution was stirred at
room temperature overnight. The solution was then slowly
poured onto crushed ice, and precipitated magnesium hydroxide
2-C-Meth yl-D-er yth r on o-1,4-la cton e (12) a n d 2-C-Meth -
yl-D-th r eon o-1,4-la cton e (13). (2R,3RS)-1,2-O-Isopropylidene-
3-O-trimethylsilyl-1,2,3-trihydroxy-3-cyano-butane (10) (12.0 g,
49.3 mmol) was suspended in 30 mL of 25% hydrochloric acid.
Ethanol (10 mL) was added to improve the solubility of the
lipophilic cyanohydrin. The reaction mixture was stirred at 45
°C for 30 min and subsequently under reflux for 3 h. The mixture
became brown, and a precipitate of ammonium chloride was
formed. The acid was neutralized with concentrated ammonia.
The mixture was evaporated to dryness. The product mass was
triturated with 50 mL of methanol. Insoluble ammonium
chloride was filtered off. Methanol was removed under reduced
pressure. The residual oil contained the lactones 12 and 13 and
the open chain carboxylic acids 11. All three compounds can be
purified on an analytical scale by column chromatography (silica,
1 cm × 30 cm) developed with EtOAc/2-propanol/water (65:24:
(28) Dumont, R.; Pfander, H. Helv. Chim. Acta 1983, 66, 814-823.
(29) Hagen, S.; Anthonsen, T.; Kilaas, L. Tetrahedron 1979, 35, 2583.

Notes
J . Org. Chem., Vol. 65, No. 2, 2000 591
12, v/v/v). Lactonization was brought to completion by boiling
the residue with 60% formic acid (30 mL) for 2 h. When no more
open chain carboxylic acids were present (detected by TLC with
lead tetraacetate), the reaction mixture was concentrated under
reduced pressure. The residual oil was dissolved in a EtOAc/2-
propanol/water (5 mL, 65:24:12, v/v/v). The solution was placed
on a column of silica gel (acidic form) and was eluted with the
EtOAc/2-propanol/water mixture. Fractions were combined and
concentrated under reduced pressure. The residue was lyophi-
lized. The residual colorless oil (5.9 g, 45 mmol, 91%) contained
2-C-methyl-D-erythrono-1,4-lactone and 2-C-methyl-D-threono-
1,4-lactone in a ratio of about 3:1 as determined by NMR
spectroscopy.
2.0 g (12 mmol, 89%) of 2,3-O-isopropylidene-2-C-methyl-D-
erythrofuranose as an anomeric mixture. 1H NMR (360 MHz,
CDCl3): δ (ppm) 1.29 (s), 1.30 (s), 1.34 (s), 1.35 (s), 1.37 (s) (18
3
2
H), 3.46 (dd, J ) 3.5 Hz, J ) 11.1 Hz, 1H), 3.55 (m, 1H), 3.78
2
2
3
(d, J ) 11.5 Hz, 2H), 3.84 (d, J ) 11.1 Hz, 1H), 3.97 (dd, J )
3.8 Hz, 2J ) 10.4 Hz, 1H), 4.29 (dd, 3J ) 3.1 Hz, 3J ) 8.9 Hz,
2H), 4.52 (d, 2J ) 11.1 Hz, 1H), 5.13 (d, 3J ) 2.7 Hz, 1H). 13C
NMR (90 MHz, CDCl3): δ (ppm) 19.4, 21.4, 26.3, 26.9, 27.2, 28.0,
67.1, 71.5, 84.9, 86.0, 86.1, 91.4, 101.4, 103.3, 112.4, 112.9. Anal.
Calcd for (C8H14O4): C, 55.2; H, 8.04. Found: C, 54.7; H, 8.11.
TLC Rf 0.61 (hexane/EtOAc 1:2 v/v).
2,3-O-Isopr opyliden e-2-C-m eth yl-D-er yth r ose-(O-ben zyl)-
oxim e (16). 2,3-O-Isopropylidene-2-C-methyl-D-erythrofuranose
(15) (0.5 g, 3 mmol) was dissolved in 12 mL of dry dichlo-
romethane. Dry pyridine (1 mL) and 0.88 g (5.5 mmol) of
O-benzylhydroxylamine hydrochloride were added in one por-
tion. The hydroxylamine dissolved within 20 min, and the
reaction mixture became turbid after 40 min. The mixture was
stirred for 15 h at room temperature and was evaporated to
dryness under reduced pressure. The residue was suspended in
a mixture of chloroform/EtOAc (1:4, v/v, 1 mL). The solution was
placed on a silica gel column (1 cm × 30 cm), and the product
was eluted with the solvent mixture. Fractions containing the
product were combined, and the solvent was removed under
reduced pressure, affording 0.53 g (1.9 mmol, 66%) of 16 as a
2-C-Meth yl-D-th r eon o-1,4-la cton e. 1H NMR (250 MHz,
CD3OD): δ (ppm) 1.30 (s, 3H), 3.92 (dd, 2J ) 4.3 Hz, 3J ) 9.2
2
3
2
Hz, 1H), 4.13 (dd, J ) 4.3 Hz, J ) 5.5 Hz, 1H), 4.44 (dd, J )
5.5 Hz, J ) 9.2 Hz, 1H). 13C NMR (63 MHz, CD3OD): δ (ppm)
3
17.9, 73.1, 78.8, 85.8, 161.8. IR (film): 1770 cm-1. Anal. Calcd
for (C5H8O4): C, 45.5; H, 6.06. Found: C, 44.9; H, 6.07. TLC Rf
22
0.79 (EtOAC/2-propanol/water 65:24:12, v/v/v). [R]D -35.9° (c
28
1.8, water) (lit. [R]D -18° (c 0.4, water)19).
2-C-Meth yl-D-er yth r on o-1,4-la cton e. 1H NMR (250 MHz,
CD3OD): δ (ppm) 1.33 (s, 3H), 4.00 (dd, 2J ) 1.8 Hz, 3J ) 4.3
2
3
2
Hz, 1H), 4.09 (dd, J ) 1.8 Hz, J ) 9.8 Hz, 1H), 4.38 (dd, J )
4.3 Hz, 3J ) 10.4 Hz, 1H). 13C NMR (63 MHz, CD3OD): δ (ppm)
21.9, 73.6, 75.0, 75.8, 164.9. IR (film): 1770 cm-1. Anal. Calcd
for (C5H8O4‚0.3H2O): C, 43.7; H, 6.26. Found: C, 43.0; H, 6.17.
1
colorless oil. H NMR (250 MHz, CDCl3): δ (ppm) 1.26 (s, 3H),
3
1.31 (s, 3H), 1.33 (s, 3H), 3.42-3.56 (m, 2H), 3.86 (dd, J ) 4.9
TLC Rf 0.62 (EtOAc/2-propanol/water 65:24:12, v/v/v). [R]D
Hz, 3J ) 6.7 Hz, 1H), 4.92 (s, 2H), 7.15-7.25 (m, 5H), 7.32 (s,
1H). 13C NMR (63 MHz, CDCl3): δ (ppm) 22.8, 26.6, 27.9, 60.7,
76.0, 80.5, 84.3, 109.4, 127.9, 128.2, 128.3, 137.2, 152.0. Anal.
Calcd for (C15H21NO4): C, 64.5; H, 7.52; N, 5.02. Found: C, 65.4;
H, 7.53; N, 5.07. TLC Rf 0.80 (CHCl3/EtOAc 1:4, v/v). [R]22D -24.0
(c 0.75, acetone).
22
25
-60.9° (c 0.6, water) (lit. [R]D -61.2 (c 0.2, water)20; -58.6° (c
0.61, water)17).
Open Chain Carboxylic Acids (Isomeric Mixture 1:1). 1H NMR
(250 MHz, D2O): δ (ppm) 1.14 (s, 3H), 1,17 (s, 3H), 3,45-3,85
(m, 6H). 13C NMR (63 MHz, D2O): δ (ppm) 19.8, 20.7, 64.9, 65.2,
70.1, 70.3, 77.8, 77.9, 182.5, 182.8. TLC Rf 0.45 (EtOAc/2-
propanol/water 65:24:12, v/v/v).
2,3-O-Isopr opyliden e-2-C-m eth yl-D-er yth r ose-(O-ben zyl)-
oxim e 4-Diben zyl P h osp h a te (17). Tribenzyl phosphite (1.3
g, 3.7 mmol) was dissolved in 20 mL of dry dichloromethane.
The solution was cooled to -20 °C. Iodine (0.96 g, 3.8 mmol)
was added in one portion. The mixture was protected from light
and was allowed to come to room temperature when the violet
color had disappeared. 2,3-O-Isopropylidene-2-C-methyl-D-eryth-
rose-(O-benzyl)oxime (18) (0.53 g, 1.9 mmol) was dissolved in
20 mL of dichloromethane, and 2.5 mL of pyridine was added.
The solution was cooled to -20 °C, and the solution of dibenzyl
iodophosphate was added slowly. The reaction mixture was
stirred for 2 h at room temperature and was washed subse-
quently with sodium hydrogen sulfate (30%, w/v, 2 × 10 mL), a
solution of sodium hydrogen carbonate (5%, w/v, 10 mL), and
water (10 mL). The organic phase was dried with magnesium
sulfate. The solution was evaporated to dryness. The residue
was suspended in a mixture of hexane/EtOAc (3:1, v/v, 2 mL).
The mixture was placed on a silica gel column (1 cm × 20 cm),
which was developed with hexane/EtOAc (3:1, v/v) until benzyl
iodide was completely washed out. The product was then eluted
with a mixture of chloroform/EtOAc (1:4, v/v). Fractions were
combined, and the solvent was removed under reduced pressure,
affording 0.73 g (1.4 mmol, 71%) of 17. 1H NMR (250 MHz,
CDCl3): δ (ppm) 1.31 (s, 3H), 1.37 (s, 3H), 1.39 (s, 3H), 3.90-
3.99 (m, 3H), 4.94 (s, 1H), 4.97-5.02 (m, 6H), 7.24-7.33 (m,
15H). 13C NMR (63 MHz, CDCl3): δ (ppm) 22.0, 26.6, 28.0, 65.3
2,3-O-Isop r op ylid en e-2-C-m et h yl-D-er yt h r on o-1,4-la c-
ton e (14). Anhydrous zinc chloride (14.1 g, 103 mmol) was
dissolved in 100 mL of acetone. The solution was cooled with
ice, and 5.9 g of a mixture of 2-C-methyl-D-erythrono-1,4-lactone
(12) (34 mmol) and 2-C-methyl-D-threono-1,4-lactone (13) (11
mmol) dissolved in 13 mL of acetone was added. After 18 h the
solution was diluted with 150 mL of chloroform. Zinc chloride
and unreacted 2-C-methyl-D-threono-1,4-lactone were removed
by washing with water (3 × 100 mL). The organic layer was
dried with magnesium sulfate, and the solvent was removed
under reduced pressure, affording pure 2,3-O-isopropylidene-2-
C-methyl-D-erythronolactone (4.4 g, 26 mmol, 76% from 2C-
methyl-D-erythrono-1,4-lactone) as a colorless oil that crystal-
lized at -20 °C. To recycle unreacted 13, the combined water
phases were lyophilized, and the solid residue was extracted
three times with 50 mL of boiling methanol. The precipitate was
filtered off, and methanol was removed under reduced pressure.
The residue was dissolved in EtOAc/2-propanol/water (65:24:
12, v/v/v, 2 mL) and was placed onto a column of silica (1 cm ×
20 cm), which was developed with the same solvent. Fractions
containing 13 were pooled and evaporated to dryness, affording
1
1.1 g of 13 as colorless oil (analytical data for 13 see above). H
NMR (360 MHz, CDCl3): δ (ppm) 1.33 (s, 3H), 1.37 (s, 3H), 1.48
(s, 3H), 4.24 (dd, 3J ) 3.54 Hz, 2J ) 11.1 Hz, 1H), 4.34 (dd, 2J )
3
2
3
2
3
11.1 Hz, J ) 0 Hz, 1H), 4.41 (dd, J ) 3.5 Hz, J ) 0 Hz, 1H).
13C NMR (90 MHz, CDCl3): δ (ppm) 18.4, 26.5, 26.9, 68.9, 80.3,
81.4, 113.0, 176.7. Anal. Calcd for (C8H12O4): C, 55.8; H, 6.97.
Found: C, 55.1; H, 7.04. TLC Rf 0.77 (CHCl3/EtOAc 1:4, v/v).
[R]22 -82.5° (c 2.1, acetone) (lit. [R]22 -40°).22
(d, J CP ) 5.5 Hz), 69.1-69.5 (m), 76.2, 80.2, 82.5 (d, J CP ) 7.9
3
Hz), 109.7, 127.9-128.5, 135.6 (d, J CP ) 6.8 Hz), 137.9, 150.3.
31P NMR (101 MHz, CDCl3): δ (ppm) -0.8 (s). HRMS(EI) calcd
for (C29H34NO7P) 539.20728, found 539.20746 ( 3.9 ppm. Anal.
Calcd for (C29H34NO7P): C, 64.6; H, 6.30; N, 2.06; P, 5.75.
Found: C, 64.5; H, 6.49; N, 2.09; P, 5.60. TLC Rf 0.32 (hexane/
D
D
2,3-O-Isopr opyliden e-2-C-m eth yl-D-er yth r ofu r an ose (15).
2,3-O-Isopropylidene-2-C-methyl-D-erythrono-1,4-lactone (14) (2.2
g, 13 mmol) was dissolved in 60 mL of dry tetrahydrofuran. The
mixture was cooled to -78 °C under an atmosphere of nitrogen.
A solution of diisobutylaluminum hydride (DIBAH) (1 M in
hexane, 17 mL, 17 mmol) was added slowly. The solution was
allowed to stand in the cooling bath overnight. Wet ether (180
mL) and wet silica gel (30 g) were added. The mixture was
stirred for 1 h and was allowed to warm to room temperature.
The mixture was then filtered. The solution was dried with
magnesium sulfate, and the solvent was removed under reduced
pressure. The residual oil was purified by chromatography on
silica gel with a mixture of hexane/EtOAc (1:2, v/v), affording
EtOAc 3:1, v/v). [R]22 -7.4 (c 1.0, acetone).
D
2,3-O-Isop r op ylid en e-2-C-m eth yl-D-er yth r ose 4-Diben zyl
P h osp h a te (18). 2,3-O-Isopropylidene-2-C-methyl-D-erythrose-
(O-benzyl)oxime 4-dibenzyl phosphate (17) (0.26 g, 0.43 mmol)
was dissolved in 15 mL of dichloromethane containing 2 mL of
pyridine. The solution was cooled to -78 °C and was ozonized
for 7 min with an ozone flow of about 3 g/min (0.4 mmol).
Nitrogen was then bubbled through the dark blue reaction
mixture. When the blue color had vanished, 2 mL of dimethyl-
sulfide was added. The mixture was allowed to stand at -78 °C
for 1 h and was then brought to room temperature. Solvent and
pyridine were removed under reduced pressure, and the crude

592 J . Org. Chem., Vol. 65, No. 2, 2000
Notes
oil was purified by column chromatography (silica gel; chloroform/
EtOAc 1:4, v/v) ,affording 0.17 g (0.39 mol, 91%) of 18. Because
of its instability 18 should be used immediately for the next
reaction step. 1H NMR (360 MHz, CDCl3): δ (ppm) 1.24 (s, 3H),
1.36 (s, 3H), 1.46 (s, 3H), 3.93-4.02 (m, 2H), 4.05-4.13 (m, 1H),
4.92-5.00 (m, 4H), 7.23-7.30 (m, 10H), 9.51 (s, 1H). 13C NMR
suspended in 1 mL of 30% acetic acid. The mixture was heated
to 70 °C for 1 h. Water and acetic acid were removed by
lyophilization, affording 50 mg (0.37 mmol, 71%) of 20 in an
anomeric mixture. 1H NMR (360 MHz, CD3OD): δ (ppm) 1.18
(s, 3H), 1.19 (s, 3H), 3.56 (dd, J ) 5.3 Hz, J ) 6.6 Hz, 1H), 3.74-
3.78 (m, 1H), 3.90-4.05 (m, 4H), 4.78 (s, 1H), 4.91 (s, 1H). 13C
NMR (90 MHz, CD3OD): δ (ppm) 22.6, 23.4, 72.5, 75.1, 75.7,
75.9, 101.9, 104.2. Anal. Calcd for (C5H10O4‚0.4H2O): C, 42.5;
H, 7.65. Found: C, 43.2; H, 7.76. TLC Rf 0.62 (EtOAc/2-propanol/
water 65:24:12, v/v/v).
2
(90 MHz, CDCl3): δ (ppm) 19.7, 26.5, 27.8, 64.3 (d, J CP ) 6.0
3
4
Hz), 69.5 (m), 82.7 (d, J CP ) 8.7 Hz), 85.1, 110.9, 126.8 (d, J CP
) 14.5 Hz), 127.9, 128.6, 135.6 (d, 3J CP ) 7.3 Hz), 202.0; 31P NMR
(101 MHz, CDCl3): δ (ppm) -1.0 (s). TLC Rf 0.23 (CHCl3/EtOAc
1.5:1, v/v).
2,3-O-Isop r op ylid en e-2-C-m eth yl-D-er yth r itol (21). 2,3-
O-isopropylidene-2-C-methyl-D-erythono-1,4-lactone (14) (2.9 g,
17 mmol) was dissolved in 100 mL of THF. The solution was
cooled to -78 °C. DIBAH (1 M in hexane, 40 mL, 40 mmol) was
added slowly. The solution was allowed to come to room
temperature, and 10 mL of water was added to destroy excess
hydride. The sticky suspension was extracted with chloroform
(4 × 50 mL). The organic phase was dried with magnesium
2,3-O-Isop r op ylid en e-2-C-m eth yl-D-er yth r itol 4-Diben -
zyl P h osp h a te (19). 2,3-O-Isopropylidene-2-C-methyl-D-eryth-
rose 4-dibenzyl phosphate (18) (85 mg, 0.20 mmol) was dissolved
in 3 mL of dry methanol, and the solution was cooled to 0 °C.
Sodium borohydride (20 mg, 0.53 mmol) was added in one
portion. The mixture was stirred for 2 h. Water (5 mL) was then
added to destroy the excess of borohydride, and the mixture was
adjusted to pH 5 with concentrated acetic acid. The suspension
was extracted 4 times with 10 mL of chloroform, and the organic
solution was washed with 20 mL of a sodium hydrogen carbonate
solution (5%, w/v). The organic phase was dried with magnesium
sulfate, and the solvent was removed under reduced pressure,
affording 86 mg (0.20 mmol, 100%) 19. 1H NMR (250 MHz,
CDCl3): δ (ppm) 1.20 (s, 3H), 1.30 (s, 3H), 1.36 (s, 3H), 1.89 (s,
broad, 2H), 3.34 (m, 2H), 3.95 (dd, J ) 4.70 Hz, J ) 7.1 Hz,
1H), 4.08-4.20 (m, 2H), 5.00 (dd, J ) 1.8 Hz, J ) 8.6 Hz, 4H),
7.29 (m, 10H). 13C NMR (63 MHz, CDCl3): δ (ppm) 22.1, 26.4,
1
sulfate and evaporated, affording 1.3 g (7.3 mmol, 43%) 21. H
NMR (250 MHz, CDCl3): δ (ppm) 1.28 (s, 3H), 1.31 (s, 3H), 1.36
(s, 3H), 3.32 (d, 2J ) 11.6 Hz, 1H), 3.53 (d, 2J ) 11.0 Hz, 1H),
3.75-3.90 (m, 3H). 13C NMR (63 MHz, CDCl3): δ (ppm) 22.6,
26.5, 28.2, 60.0, 65.1, 81.7, 82.4, 107.8. Anal. Calcd for
(C8H16O4): C, 54.6; H, 9.09. Found: C, 53.9; h, 9.35. TLC Rf 0.33
(hexane/EtOAc 3:1 v/v). [R]22 -26.0° (c 0.36, CH2Cl2) (lit. [R]578
D
+7.92 (c 0.48, CHCl3)15).
2-C-Met h yl-D-er yt h r it ol (22). 2,3-O-Isopropylidene-2-C-
methyl-D-erythritol (21) (0.44 g, 2.5 mmol) was dissolved in a
mixture containing water (10 mL), acetone (5 mL), and glacial
acetic acid (2 mL). The mixture was heated to 60 °C for 3 h.
The solvent was then removed by lyophilization, and the
colorless residue (340 mg) was dissolved in a mixture of EtOAc/
2-propanol/water (1 mL, 65:24:12, v/v/v). The solution was placed
on a silica gel column (1 cm × 20 cm) and eluted with the same
solvent. Fractions containing the product were pooled, and the
solvent was removed under reduced pressure, affording 0.12 g
(0.88 mmol, 35%) of 22. 1H NMR (200 MHz, D2O): δ (ppm) 1.09
(s, 3H), 3.43 (d, 2J ) 11.8 Hz, 1H), 3.55 (d, 2J ) 11.8 Hz, 1H),
2
2
2
28.1, 65.0, 65.2 (d, J CP ) 5.5 Hz), 69.4 (dd, J CP ) 2.7 Hz, J CP
) 5.5 Hz), 81.1 (d, 3J CP ) 8.2 Hz), 81.7, 108.5, 126.9, 128.6, 135.6
(d, J CP ) 6.8 Hz). 31P NMR (101 MHz, CDCl3): δ (ppm) 0.5 (s).
3
Anal. Calcd for (C22H29O7P): C, 60.6; H, 6.65; P, 7.11. Found:
C, 59.8; H, 6.53; P, 6.83. TLC Rf 0.65 (CHCl3/EtOAc 1.5:1, v/v).
2-C-Meth yl-D-er yth r itol 4-P h osp h or ic Acid (5). 2,3-O-
Isopropylidene-2-C-methyl-D-erythritol 4-dibenzyl phosphate (19)
(86 mg, 0.20 mmol) was suspended in 8 mL of a mixture
containing 4 mL of methanol and 4 mL of water. A catalytic
amount of palladium on charcoal was added, and the suspension
was hydrogenated for 20 h at atmospheric pressure. The catalyst
was removed by filtration through a 0.2 µm membrane filter.
The acidic solution (pH 2) was heated to 70 °C for 60 min.
Methanol was removed under reduced pressure at 40 °C, and
the residue was lyophilized, affording 35.3 mg (163 µmol, 83%)
of the phosphoric acid that was essentially pure (>95%). For
enzymatic procedures 5 was further purified by HPLC. The
phosphoric acid was dissolved in 1 mL of water. The solution
was placed on a Nucleosil SB10 HPLC column and was eluted
with 0.5 M formic acid at a flow rate of 1 mL/min. The effluent
was monitored refractometrically. Fractions containing the
product (retention volume 15 mL) were pooled and freeze-dried,
3.50-3.65 (m, 2H), 3.81 (dd, 2J ) 10.1 Hz, 3J ) 1.5 Hz, 1H). 13
C
NMR (63 MHz, D2O): δ (ppm) 21.4, 65.0, 69.3, 77.1, 77.9. Anal.
Calcd for (C5H12O4‚0.16D2O): C, 43.1; H, 9.08. Found: C, 43.1;
H, 9.15. TLC Rf 0.44 (EtOAc/2-propanol/water 65:24:12, v/v/v).
[R]22 +9.0° (c 1.0, water) (lit. [R]28 +21.4° (c 7.0, water)23; [R]D
D
D
+19.6° (c 0.1, water)24).
Ack n ow led gm en t. This work was supported by
grants from the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen Industrie. We thank Ange-
lika Werner for the skillful help with this manuscript
and the Institut fu¨r Anorganische Chemie, Technische
Universita¨t Mu¨nchen for help with the elemental analy-
sis.
1
affording 18.0 mg of pure 5. H NMR (500 MHz, D2O, pH 1): δ
2
2
(ppm) 1.04 (s, 3H), 3.37 (d, J ) 11.8 Hz, 1H), 3.50 (d, J ) 11.8
Hz, 1H), 3.64 (dd, 3J ) 2.6 Hz, 3J ) 8.1 Hz, 1H), 3.77 (ddd, 3J HP
) 6.2 Hz, 3J ) 8.1 Hz, 3J ) 10.8 Hz, 1H), 4.01 (ddd, 3J ) 2.5 Hz,
3J HP ) 6.0 Hz, J ) 10.8 Hz, 1H). 13C NMR (125 MHz, D2O, pH
3
1): δ (ppm) 18.2 (C′2), 65.9 (d, 2J CP ) 5.1 Hz, C4), 66.2 (C1), 73.1
(d, J CP ) 7.6 Hz, C3), 73.8 (C2). 31P NMR (101 MHz, D2O, pH
3
Su p p or tin g In for m a tion Ava ila ble: NMR spectra (1H,
13C, DEPT, 31P, or NOESY) for compounds 5 and 7-22. This
material is available free of charge via the Internet at
http://pubs.acs.org.
1): δ (ppm) 3.7 (s). Anal. Calcd for (C5H13O7P‚HCOOH‚0.2H3-
PO4‚0.4H2O): C, 24.9; H, 5.74; P, 13.5. Found: C, 24.9; H, 5.76;
P, 13.4.
2-C-Meth yl-D-er yth r ofu r a n ose (20). 2,3-O-Isopropylidene-
2-C-methyl-D-erythrofuranose (15) (90 mg, 0.52 mmol) was
J O9905118