Highly deoxygenated sugars. I. C2-branched glucose derivatives and carbon linked deoxygenated disaccharides

Article abstract of DOI:10.1081/CAR-120014904

Triacetylglucal (1) is converted with high α-selectivity (>9:1) to the corresponding 2,3-unsaturated allyl and benzyl glycosides 2 and 3 using ferric chloride as the catalyst. The 6-O-silyl-protected allylic alcohol 5 is transformed to the 3,4-unsaturated C2-branched ester 6 or the amide 7 by Claisen rearrangement. The highly deoxygenated iodo lactone 8, resulting from the amide 6 by iodolactonization, is a versatile starting material for chiral building blocks 9-12. The 3,4-unsaturated C2-branched ester 6 is reduced to the aldehyde 14 and converted to a carbon linked disaccharide analogue 16 via cycloaddition with Danishefky's diene.

Full text of DOI:10.1081/CAR-120014904

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HIGHLY DEOXYGENATED SUGARS. I. C2-BRANCHED
GLUCOSE DERIVATIVES AND CARBON LINKED
DEOXYGENATED DISACCHARIDES *
Karsten Krohn a , Ulrich Flörke a & Dietmar Gehle a
a Fachbereich Chemie und Chemietechnik, Universität Paderborn, Warburger Str. 100,
Paderborn, 33098, Germany
Published online: 21 Aug 2006.
To cite this article: Karsten Krohn , Ulrich Flörke & Dietmar Gehle (2002): HIGHLY DEOXYGENATED SUGARS. I. C2-BRANCHED
GLUCOSE DERIVATIVES AND CARBON LINKED DEOXYGENATED DISACCHARIDES * , Journal of Carbohydrate Chemistry, 21:5,
431-443
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JOURNAL OF CARBOHYDRATE CHEMISTRY
Vol. 21, No. 5, pp. 431–443, 2002
HIGHLY DEOXYGENATED
SUGARS. I. C2-BRANCHED GLUCOSE
DERIVATIVES AND CARBON LINKED
DEOXYGENATED DISACCHARIDES*
Karsten Krohn,y Ulrich Flo¨rke, and Dietmar Gehle
Fachbereich Chemie und Chemietechnik, Universita¨t Paderborn,
Warburger Str. 100, 33098 Paderborn, Germany
ABSTRACT
Triacetylglucal (1) is converted with high a-selectivity ( >9:1) to the cor-
responding 2,3-unsaturated allyl and benzyl glycosides 2 and 3 using ferric
chloride as the catalyst. The 6-O-silyl-protected allylic alcohol 5 is trans-
formed to the 3,4-unsaturated C2-branched ester 6 or the amide 7 by Claisen
rearrangement. The highly deoxygenated iodo lactone 8, resulting from the
amide 6 by iodolactonization, is a versatile starting material for chiral build-
ing blocks 9–12. The 3,4-unsaturated C2-branched ester 6 is reduced to the
aldehyde 14 and converted to a carbon linked disaccharide analogue 16 via
cycloaddition with Danishefky’s diene.
Key Words: Ferrier rearrangement; Claisen rearrangement; Branched
sugars; Hetero Diels–Alder reaction; C-linked disaccharide
*
Dedicated to Professor Dr. Dr. h.c. Frieder Lichtenthaler on the occasion of his 70th birthday.
yCorresponding author. E-mail: kk@chemie.uni-paderborn.de
431
DOI: 10.1081/CAR-120014904
0732-8303 (Print); 1532-2327 (Online)
www.dekker.com
Copyright D 2002 by Marcel Dekker, Inc.

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KROHN, FLORKE, AND GEHLE
432
[3]
[4]
Table 1. Comparison of FeCl3 and Sc(OTf)3 as the Catalysts in the Ferrier Rearrangement
with Glucal Acetate 1
Entry
Alcohol
Cat. [mol equiv.]
Yield
a/b Selectivity
Time
1
2
3
4
Allyl alcohol
Allyl alcohol
Benzyl alcohol
Benzyl alcohol
FeCl3 [0.01]
87%
85%
93%
87%
10:1
5:1
9:1
7:1
30 min.
2.5 h
Sc(OTf)3 [0.05]
FeCl3 [0.01]
Sc(OTf)3 [0.05]
15 min.
1.5 h
In connection with a new project on the utilization of sugars as starting materials
for highly deoxygenated chiral building blocks, we investigated the synthesis of C-2
alkylated sugars[1] obtained by Claisen rearrangement[2] of allyl alcohol 5. Fortunately,
[3]
[4]
two highly effective new catalysts, FeCl3 and Sc(OTf)3 were recently proposed for
the Ferrier type II rearrangement to prepare the allyl acetates 2 and 3 starting from
glucal acetate 1. With these Lewis acids, much milder reaction conditions and better
yields were obtained than described with the previously used boron trifluoride ethe-
rate[5] or other catalysts (review[6]). Thus, the first task was to find the best conditions
with respect to the anomeric ratio of the glycosides a-2 and b-3, determined by GC
analysis. Both catalysts FeCl3 and Sc(OTf)3 were compared, with allyl and benzyl
alcohol and glucal acetate 1 as the substrates. The results are summarized in Table 1.
The data clearly show the superiority of FeCl3 over Sc(OTf)3 with respect to yield,
anomeric ratio and shorter reaction times under the conditions used. In particular, the
high predominance of the a-anomers 2 was important for the purity of all subsequent
products. It was possible to obtain the starting material 2a and 2b as pure a-anomers in
crystalline form and record the spectroscopic data and optical rotation. The reaction
was also amenable to scale-up and the pure anomers 2a and 2b were isolated in multi-
gram quantities (Scheme 1).
The free hydroxyl group was required for the anticipated Claisen rearrangements.
This was easily achieved by Zemple´n saponification of the esters of the anomeric
Scheme 1. Fe(Cl)3-catalysed Ferrier reaction of glucal acetale (1) and selective protection as TBS
ether 5.

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HIGHLY DEOXYGENATED SUGARS. I
433
mixture 2b/3b. The pure deacetylated a-anomer 4 was obtained by chromatography and
crystallization. Protection of the primary hydroxyl group at C-6 of 4 was then easily
achieved by selective silylation as tert-butyldimethylsilyl ether 5.
Claisen type rearrangements are often used in the synthesis of branched sugars
(reviews[1,2]). For instance, Corey has introduced C-4 substitution using the Eschen-
moser variation in his famous enantioselective prostaglandin synthesis.[7] In our case,
we tested the Johnson[8] and Eschenmoser[9] variations on the C-4 allyl alcohol 5 to
arrive at substitution at C-2. Previously, C-2 branching was investigated by Ferrier,[10]
employing the corresponding vinyl ethers of related C-4 allyl alcohols. However, the
yield in this mercury-catalyzed preparation of the corresponding vinyl alcohol was low
(30%). Reaction of allyl alcohol 5 with an eightfold excess of orthoacetic ester with
catalytic amounts of propionic acid in boiling xylene afforded the ester 6 in 86% yield
as one single isomer. The related reaction under Eschenmoser conditions using only 1.5
equiv. of N,N-dimethylacetamide dimethyl diacetal gave an 89% yield of the corres-
ponding amide 7. Both the ester 6 and the amide 7 are ideally suited for the inves-
tigation of further transformations to afford useful chiral building blocks.
First, the iodolactonization was tried with both the ester 6 and the amide 7. Much
better yields (76%) of the lactone 8 were obtained with the amide 7. It has to be
stressed that the iodolactone 8 possesses a highly condensed array of six functional
groups, all of them of different reactivity or orthogonal protection. In Scheme 2, a
number of simple transformations of 8 are shown. First, the fluoride mediated cleavage
of the silyl ether liberated the primary hydroxyl group to afford the alcohol 9. All of
the transformations en route from 4 to 9 were stereospecific and, not surprisingly, only
Scheme 2. a) TBAF, THF, 30 min, 86%; b) DBU, CH2Cl2, 10 h at 20°C, 78%; c) MeOH, KOH,
H2O, 1 h, 93%; d) LAH, THF, 1 h, 86%.

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KROHN, FLORKE, AND GEHLE
434
Figure 1. Molecular structure of 9.
one stereoisomer was obtained, as confirmed by X-ray structure analysis of 9 as shown
in Figure 1.
Elimination of hydrogen iodide and opening of the lactone 8 to yield the hydroxy
acid 10 was achieved by treatment with DBU followed by aqueous methanolic
potassium hydroxide. This saponification also proved the location of the 5,6-C
C
double bond chemically. Reductive opening without elimination to yield the diol 11
could be achieved using DIBAH or LAH. Substitution of the iodide with both hetero
and carbon based nucleophiles was not successful. Instead, elimination to the lactone
olefin 12 took place. This elimination was best achieved using DBU as the base.
Scheme 3. Conversion of ester 6 to the aldehyde 14 and cycloaddition with Danishefky’s diene to
yield 16.

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HIGHLY DEOXYGENATED SUGARS. I
435
Finally, we wanted to demonstrate the utility of the C-2-branched glucose de-
rivative 6 in the synthesis of carbon linked disaccharide analogues such as 16. The
synthetic scheme envisioned the reduction of the ester 6 to an aldehyde 14, suitable for
a hetero Diels–Alder reaction[11] using Danishefsky’s diene 15.[12] Thus, the ester 6 was
reduced with LAH to the alcohol 13 (93%) and then oxidized with PCC[13] in 92% yield
to the aldehyde 14 (Scheme 3). Different catalysts were tried for the hetero Diels–Alder
reaction of 14 with 15. Using ZnCl2,[14] a 77% yield (at 63% conversion) of a major
product 16 was obtained after 8 h of reaction time and acidic work up. The intermediate
Diels–Alder adduct was not isolated but eliminated to the enone 16 upon acidic
workup. Analysis of the NMR spectra of 16 revealed the presence of a ca. 1:1 mixture
of diastereoisomers. The stereoselectivity could not be improved employing the chiral
shift reagent Eu(fod)3,[15] yielding 47% (at 66% conversion) of 16 in a slow reaction.
In summary, we have demonstrated that selectively protected products of the
Ferrier rearrangement 5 can be transformed in only one step to C-2 branched un-
saturated sugars 6 or 7, which are both starting materials for a great variety of highly
functionalized chiral building blocks 8–16.
EXPERIMENTAL
General remarks and instrumentation. Silica gel 60 F254 coated plates from
Merck AG Darmstadt were used for TLC. Spots were detected by UV light (l =254
and 366 nm), spraying and heating with 8% ethanolic sulfuric acid or the ce-
rium(IV)molybdato phosphoric acid reagent (Merck AG). Preparative LC were per-
formed using silica gel plates (1 mm) from Macherey und Nagel. Melting points were
recorded with a Gallenkamp Melting Point apparatus (uncorrected); IR spectra:
NICOLET 510 P; optical rotations: Perkin–Elmer polarimeter 241 (589 nm); elemental
analyses: Perkin–Elmer Elementar Analysator 240; mass spectra: FINNIGAN MAT
8200 and FISON MD 800, relative intensities in brackets; NMR spectra: Bruker ARX
200 (200/50 MHz) and Bruker AMX 300 (300/75 MHz) spectrometer. GC: Hewlett
Packard 5890 Series II, column: FS-SE-52.
General procedure for the ferrier rearrangements. To a solution of 3,4,6-tri-
O-acetyl-D-glucal (ca. 5 mmol) and the corresponding alcohol (1.1 equiv.) in CH2Cl2
[3]
[4]
was added a 0.1 M solution of FeCl3 (0.01 equiv. in CH2Cl2) or Sc(OTf)3 (0.25
mmol or 0.05 equiv.). The reaction was monitored by TLC [ca. 30 min for FeCl3, ca. 2
h for Sc(OTf)3] and then quenched by addition of aqueous NaHCO3 solution (100 mL).
The phases were separated, the aqueous phase was extracted twice with CH2Cl2, and
the combined organic phases were washed with brine (50 mL), dried (MgSO4), and the
solvent removed under reduced pressure. The crude mixture was analyzed by GC. The
mixture was chromatographed on silica gel or crystallized to obtain the pure a-ano-
mers. For yields and conditions see Table 1 and individual compounds.
Allyl-4,6-di-O-acetyl-2,3-dideoxy-a-D-erythro-hex-2-enopyranoside (2a). 3,4,
6-Tri-O-acetyl-D-glucal (5.0 g, 18.4 mmol), allyl alcohol (1.4 mL, 20 mmol) in
CH2Cl2 (100 mL), 0.1 M of FeCl3 (1.9 mL). Mp 42–43°C (MeOH/hexane) (ref. mp
44–46°C),[16] [a]D + 115.5°, (c 1.00, CHCl3) (ref. [a]D = +111.5°, (c 1.20, CHCl3)).[16]

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KROHN, FLORKE, AND GEHLE
436
Benzyl-4,6-di-O-acetyl-2,3-dideoxy-a-D-erythro-hex-2-enopyranoside
(2b). 3,4,6-Tri-O-acetyl-D-glucal (5.0 g, 18.4 mmol), benzylic alcohol (2.4 mL, 20
mmol) in CH2Cl2 (100 mL), 0.1 of M FeCl3 (1.9 mL). [a]D +75.3°, (c 1.04, MeOH);
mp 34.5°C. 1H NMR (200 MHz, CDCl3): d= 2.10, (s, 3H, COCH3), 2.12 (s, 3H,
COCH3), 4.09–4.36 (m, 3H, 5-H, 6-H), 4.63 (d, J7a,7b =12.1 Hz, 1H, 7a-H), 4.85, (d,
J7a,7b =12.1 Hz, 1H, 7b-H), 5.16 (br s, 1H, 1-H), 5.36 (m, 1H, 4-H), 5.88–5.94 (m, 2H,
2-H, 3-H), 7.31–7.45 (m, 5H, Ar-H). 13C NMR (50 MHz, CDCl3): d =21.2 (q,
COCH3), 21.4 (q, COCH3), 63.4 (t, C-6), 65.7 (d, C-5), 67.5 (d, C-4), 70.7 (t, C-7),
94.1 (d, C-1), 127.9 (d, C-arom.), 128.2 (d, C-arom.), 128.3 (d, C-arom.), 128.5 (d, C-
arom.), 128.9 (d, C-arom.), 129.4, (d, C-2), 129.7 (d, C-3), 138.0 (s, C-arom.), 170.7,
(s, CO), 171.2 (s, CO). MS (CI, i-Bu), m/z (%): 320 (1) [M + ], 261 (9), 213 (100), 153
(34), 111 (5), 91 (14), 57 (8), 43 (12).
Anal. Calcd for C17H20O6: C, 63.74; H, 6.29. Found: C, 63.89; H, 6.46.
Benzyl-2,3-dideoxy-a-D-glycero-hex-2-enopyranoside (4). A small piece of
sodium (0.02 g, 0.9 mmol) was added to a solution of 2b/3b (ca. 9:1, 1.00 g, 3.13
mmol) in methanol (50 mL). The reaction was monitored by TLC and adjusted to pH 7
after 2 h by addition of Amberlite IR-120. The solvent was removed under reduced
pressure not exceeding an external temperature of 35°C. The residue was dried at 0.1
mm Hg to afford crude 4 (0.71 g, 95%). The anomeric mixture was separated by
column chromatography on silica gel (CH2Cl2/2% MeOH) and crystallized from
MeOH/hexane. Mp 85–87°C (ref. mp 88–90°C);[17] [a]D +48.4°, (c 1.03, CHCl3); (ref.
[a]D +49°, (c 1.01, CHCl3)).[17]
Benzyl-6-O-(tert-butyldimethylsilyl)-2,3-dideoxy-a-D-glycero-hex-2-enopyrano-
side (5). A solution of the diol 4 (800 mg, 3.38 mmol) in dry CH2Cl2 (50 mL) was
treated with imidazole (2 equiv., 460 mg, 5.07 mmol). To this mixture was added at
0°C a solution of tert-butyldimethylsilyl chloride (TBSCl) (609 mg, 4.06 mmol, 1.2
equiv.) in dry CH2Cl2 (10 mL) and the solution was stirred for 3 h (TLC monitoring).
The solution was quenched by addition of aqueous NaHCO3 (50 mL) and extracted
with CH2Cl2 (2 ꢀ 20 mL). The combined organic phases were washed with brine (10
mL), dried (MgSO4), filtered, and the solvent removed under reduced pressure to afford
5 (92%, 896 mg) as a colorless oil. [a]D =35.7°, (c 1.05, EtOH); (ref. [a]D + 30.4°,
(c 1.03, EtOH)).[17]
Anal. Calcd for C19H30O4Si: C, 65.10; H, 8.83. Found: C, 65.04; H, 8.95.
Ethyl [2-Benzyloxy-6-(tert-butyldimethylsilanyloxymethyl)-3,6-dihydro-2H-
pyran-3-yl]-acetate (6). A solution of allyl alcohol 5 (3.00 g) in xylene (200 mL)
was treated with an eightfold excess of triethyl orthoacetate (10 mL) and propionic acid
(0.5 mL). The mixture was refluxed for 2 d, the solvent removed under reduced pressure,
and the residue purified by column chromatography on silica gel (petroleum ether:ethyl
acetate = 15:1) to yield ester 6 (1.7 g, 86%) and 1.36 g of unreacted starting material 5
(55% conversion). [a]D +6.1°, (c 2.20, MeOH). IR (Film): n [cm ꢁ 1] =2955 (C H),
2929 (C H), 2884 (C H), 2856 (C H), 1729 (C O, ester), 1652 (C C), 1628
1
(C C), 1488 (C H), 1388 (C H), 1258 (C O), 1090 (C O). H NMR (300 MHz,
CDCl3): d= 0.11 (s, 6H, Si(CH3)2), 0.93 (s, 9H, C(CH3)3), 1.22 (t, J11,10 =7.2 Hz, 3H, 11-
H), 2.39 (dd, J8a,2 = 7.2 Hz, J8a,8b = 16.2 Hz, 1H, 8a-H), 2.57 (dd, J8b,2 =8.1 Hz,

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HIGHLY DEOXYGENATED SUGARS. I
437
J8a,8b = 16.2 Hz, 1H, 8b-H), 2.97 (m, 1H, 2-H), 3.54 (m, 2H, 6-H), 4.08 (q, J10,11 = 7.1 Hz,
2H, 10-H), 4.23 (m, 1H, 5-H), 4.57 (d, J7a,7b =11.7 Hz, 1H, 7a-H), 4.79 (d, J7a,7b =11.7
Hz, 1H, 7b-H), 5.11 (d, J1,2 = 4.2 Hz, 1H, 1-H), 5.66 (m, 1H, 3-H), 5.82 (m, 1H, 4-H),
7.33–7.35 (m, 5H, Ar-H). 13C NMR (75 MHz, CDCl3): d= ꢁ 5.50 (q, SiCH3), ꢁ 5.45
(q, SiCH3), 14.0 (q, C-11), 18.2 (s, SiC), 26.2 (q, C(CH3)3), 35.2 (d, C-2), 35.5 (t, C-8),
60.7 (t, C-10), 66.0 (t, C-6), 69.5 (t, C-7), 69.8 (d, C-5), 96.5 (d, C-1), 126.34 (d, C-3),
126.9 (d, C-4), 128.0 (d, C-arom.), 128.3 (d, C-arom.), 128.7 (d, C-arom.), 138.3 (s, C-
arom.), 172.6 (s, C-9). MS (EI, 70 eV, 200°C), m/z (%): 422 (2), 363 (7), 313 (6), 255
(47), 227 (10), 195 (12), 167 (7), 105 (63), 91 (100), 75 (27), 73 (23), 65 (6), 57 (7).
Anal. Calcd for C23H36O5Si: C, 65.68; H, 8.63. Found: C, 65.65; H, 8.73.
2-[2-Benzyloxy-6-(tert-butyldimethylsilanyloxymethyl)-3,6-dihydro-2H-pyran-
3-yl]-N,N-dimethylacetamide (7). The reaction was performed as described for 6 with
2.00 g of 5, N,N-dimethylacetamide dimethyl acetal (1.4 mL of a 90% solution in
hexane, 8.6 mmol, 1.5 equiv). The mixture was slowly heated within 2 h to the boiling
point and refluxed for 12 h. Column chromatography on silica gel (petroleum ether:ethyl
acetate =15:1 to 5:1) afforded 7 (2.10 g, 89%) as an oil. [a]D ꢁ 4.6°, (c 1.08, MeOH). IR
(Film): n [cm ꢁ 1]= 3063 (C H), 2950 (C H), 2929 (C H), 2857 C H), 1641
(C O, amide), 1497 (C C), 1471 (C C), 1398 (C H), 1264 (C O), 1098 (C O),
1
1021 (C
C
H). H NMR (200 MHz, CDCl3): d =0.11 (s, 6H, Si(CH3)2), 0.94 (s, 9H,
C(CH3)3), 2.27 (dd, J8a,2 =6.5 Hz, J8a,8b =16.1 Hz, 1H, 8a-H), 2.57 (dd, J8b,2 =8.1 Hz,
J8a,8b = 16.1 Hz, 1H, 8b-H), 2.92, (s, 3H, 10-H),* 2.95 (s, 3H, 11-H),* 3.10 (m, 1H, 2-H),
3.66 (dd, J6a,5 =6.5 Hz, J6a,6b =10.5 Hz, 1H, 6a-H), 3.79 (dd, J6b,5 =6.5 Hz, J6a,6b =10.5
Hz, 1H, 6b-H), 4.26 (m, 1H, 5-H), 4.55 (d, J7a,7b = 12.1 Hz, 1H, 7a-H), 4.82
(d, J7a,7b =12.1 Hz, 1H, 7b-H), 5.16 (d, J1,2 = 4.8 Hz, 1H, 1-H), 5.79 (m, 1H, 3-H),
5.84 (m, 1H, 4-H), 7.29–7.37 (m, 5H, Ar-H). 13C NMR (50 MHz, CDCl3): d= ꢁ 4.85
(q, SiCH3), ꢁ 4.78 (q, SiCH3), 18.8 (s, SiC), 26.2 (q, C(CH3)3), 34.1 (t, C-8), 37.6
(d, C-2), 35.5 (q, C-10)*, 35.8 (q, C-11)*, 66.1 (t, C-6), 69.8 (d, C-5) 69.8 (t, C-7), 97.2
(d, C-1), 126.7 (d, C-3), 127.5 (d, C-4), 128.0 (d, C-arom.), 128.5 (d, C-arom.), 128.7
*
(d, C-arom.), 138.6 (s, C-arom.), 172.7 (s, C-9). These signals could not be assigned.
MS (EI, 70 eV, 200°C), m/z (%): 420 (2) [M + H+ ], 362 (30), 332 (4), 274 (30), 254 (70),
226 (34), 180 (28), 166 (100), 122 (18), 91 (12).
Anal. Calcd for C23H37NO4Si: C, 65.83; H, 8.89; N 3.34. Found: C, 65.30; H,
9.21; N 3.26.
4-Benzyloxy-6-(tert-butyldimethylsilanyloxymethyl)-7-iodotetrahydrofu-
ro[3,2-c] pyran-2-one (8). A solution of amide 7 (1.00 g, 2.4 mmol) in a 3:1 mixture
of THF/water (50 mL) was treated with I2 (900 mg, 3.5 mmol, 1.5 equiv.) at 0 °C and
the mixture was then stirred for 12 h at 20°C. The solution was washed with a 10%
aqueous solution of sodium thiosulfate (100 mL), the phases were separated, and the
aqueous phase was extracted with dichloromethane (2 ꢀ 35 mL). The combined organic
phases were washed with brine (35 mL), dried (MgSO4), and the solvent removed
under reduced pressure. The residue was purified by column chromatography on silica
(petroleum ether:ethyl acetate=9:1) to afford the lactone 8 (920 g, 76%) as an oil.
[a]D +90.1°, (c 0.95, MeOH). IR (Film): n [cm ꢁ 1] =2955 (m, C H), 2924 (m, C H),
2857 (m, C H), 1791 (s, C O, lactone), 1471 (w, C C), 1264 (w, C C), 1155
1
(s, C O), 1107 (s, C O), 835, 772. H NMR (200 MHz, CDCl3): d =0.11 (s, 6H,

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KROHN, FLORKE, AND GEHLE
438
Si(CH3)2), 0.93 (s, 9H, C(CH3)3), 2.56 (m, 2H, 8-H), 3.05 (m, 1H, 2-H), 3.35 (m, 1H,
5-H), 3.50 (dd, J6a,5 = 6.2 Hz, J6a,6b =10.4 Hz, 1H, 6a-H), 3.68 (dd, J6b,5 =6.1 Hz,
J6a,6b =10.4 Hz, 1H, 6b-H), 4.55 (d, J7a,7b =12.3 Hz, 1H, 7a-H), 4.69 (br s, 1H, 4-H),
4.78 (d, J7a,7b = 12.3 Hz, 1H, 7b-H), 4.92 (m, 1H, 3-H), 4.97 (d, J1,2 = 5.4 Hz, 1H, 1-H),
7.28-7.42 (m, 5H, Ar-H). 13C NMR (50 MHz, CDCl3): d= ꢁ 5.0 (q, SiCH3), ꢁ 4.9
(q, SiCH3), 18.6 (s, SiC), 26.4 (q, C(CH3)3), 29.7 (d, C-4), 33.6 (t, C-8), 34.7 (d, C-2),
63.8 (d, C-5), 67.8 (t, C-6) 69.7 (t, C-7), 81.7 (d, C-3), 96.0 (d, C-1), 128.1 (d, C-
arom.), 128.5 (d, C-arom.), 128.9 (d, C-arom.), 137.2 (s, C-arom.), 176.3 (s, C-9). MS
(EI, 70 eV, 200°C), m/z (%): 288 (43), 270 (58), 231 (37), 158 (36), 130 (39), 91 (52),
65 (37), 60 (100), 42 (51), 30 (51).
Anal. Calcd for C21H31IO5Si: C, 48.65; H, 6.03. Found: C, 49.06; H, 6.10.
4-Benzyloxy-6-hydroxymethyl-7-iodotetrahydrofuro[3,2-c]pyran-2-one
(9). A solution of the iodolactone 8 (400 mg, 0.77 mmol) in dry THF (50 mL) was
treated in small portions with TBAF (290 mg, 0.92 mmol, 1.2 equiv.) and the mixture
was stirred for 30 min (TLC monitoring). The reaction was quenched by addition of
water (40 mL) and the mixture was extracted with diethyl ether (3 ꢀ 20 mL). The
combined organic phases were washed with brine (5 mL), dried (MgSO4), and the
solvent removed under reduced pressure to yield a solid that was recrystallized from
EtOAc/pentane to yield the alcohol 9 (266 mg, 86%) as colorless needles. Mp 163°C;
[a]D +121.1°, (c 0.97, MeOH). IR (KBr): n [cm ꢁ 1] =3457 (OH), 2909 (C H), 2862
(C H), 1776 (C O, lactone), 1426 (C C), 1424 (C C), 1258 (C H), 1145
1
(C O), 1097 (C O). H NMR (200 MHz, CDCl3): d= 1.93 (br, 1H, OH), 2.59 (m,
2H, 8-H), 3.05 (m, 1H, 2-H), 3.44 (m, 1H, 5-H), 3.57 (m, 1H, 6a-H), 3.77 (m, 1H, 6b-H),
4.54 (d, J7a,7b =12.3 Hz, 1H, 7a-H), 4.61 (br s, 1H, 4-H), 4.80 (d, J7a,7b = 12.3 Hz, 1H,
7b-H), 4.86 (m, 1H, 3-H), 4.99 (d, J1,2 = 5.7 Hz, 1H, 1-H), 7.28–7.45 (m, 5H, Ar-H).
13C NMR (50 MHz, CDCl3): d=27.8 (d, C-4), 33.6 (t, C-8), 34.6 (d, C-2), 63.9
(d, C-5), 68.2 (t, C-6), 69.9 (t, C-7), 81.7 (d, C-3), 96.1 (d, C-1), 128.1 (d, C-arom.),
128.4 (d, C-arom.), 129.0 (d, C-arom.), 137.0 (s, C-arom.), 176.3 (s, C-9). MS (EI, 70
eV, 200°C), m/z (%): 404 (2) [M + ], 373 (3), 279 (5), 201 (5), 171 (50), 141 (10),
108 (71), 91 (100), 65 (28), 57 (12).
Anal. Calcd for C15H17IO5: C, 44.57; H, 4.24. Found: C, 44.72; H, 4.42.
Crystal structure determination of 9:[18] C15H17IO5, Mr = 404.2, monoclinic,
˚
space group P 21, a = 9.511(2), b = 5.699(2), c = 15.210(5) A, b= 106.85(1)°,
3
3
˚
V =789.0(4) A , Z= 2, Dx = 1.701 g/cm , F(000) = 400, T= 293(2) K. Bruker-AXSꢁP14
˚
diffractometer, graphite monochromator, l(MoKa) = 0.71073 A, m= 2.05 mm
,
colorless crystal, size 0.50 ꢀ 0.22 ꢀ 0.07 mm3, o scans, 4184 intensities collected
4< 2y<55°, ꢁ 12< h< 12, ꢁ 7 <k< 7, ꢁ 19<l < 19, 3 standards every 397 reflections
showed only random deviations, Lp correction, face indexed absorption correction,
3663 unique intensities (Rint =0.017). Structure solved by direct methods, full-matrix
least-squares refinement based on F2 and 191 parameters, all but H atoms refined
anisotropically, H atoms refined with riding model on idealized positions with U =1.5
U
iso(O) and 1.2 Uiso(C). Refinement converged at R1(F)=0.062, wR2(F2, all data) =
0.172, S =1.07, absolute structure parameter (Flack) ꢁ 0.04(6), max(d/s) <0.001, min/
3
˚
max height in final DF map ꢁ 0.90/1.19 e/A (near I position). Figure 1 shows the
molecular structure. Programs used: SHELXTL.[19]

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HIGHLY DEOXYGENATED SUGARS. I
439
[2-Benzyloxy-6-(tert-butyldimethylsilanyloxymethyl)-4-hydroxy-3,4-dihydro-
2H-pyran-3-yl]-acetic acid (10). A solution of the unsaturated lactone 12 (200 mg) in
dry THF (50 mL) was treated at 20°C with methanolic KOH (1 mol/L), 6 mL) and the
mixture was stirred for 1 h (TLC monitoring). The solution was the adjusted to pH 7 by
addition of 10% HCl and extracted diethyl ether (3 ꢀ 20 mL). The combined organic
phases were washed with brine, dried (MgSO4), and the solvent removed under reduced
pressure to yield the acid 10 (198 mg, 93%) as a colorless oil. [a]D +76.9°, (c 1.0,
MeOH). IR (Film): n [cm ꢁ 1] = 2955 (C H), 2924 (C H), 2862 (C H), 1735 (C O,
1
acid), 1450 (C C), 1419 (C C), 1259 (C O), 1119 (C O). H NMR (200 MHz,
CDCl3): d =0.13 (s, 6H, Si(CH3)2), 0.96 (s, 9H, C(CH3)3), 2.49 (m, 1H, 2-H), 2.64 (dd,
J8a,2 = 6.7 Hz, J8a,8b = 16.7 Hz, 1H, 8a-H), 2.92 (dd, J8b,2 = 7.4.Hz, J8a,8b =16.7 Hz, 1H,
8b-H), 4.07 (br s, 3H, 3-H, 6-H), 4.56 (d, J7a,7b =12.0 Hz, 1H, 7a-H), 4.80 (d,
J7a,7b = 12.0 Hz, 1H, 7b-H), 5.26 (br s, 1H, 1-H), 5.35 (d, J4,3 =5.4 Hz, 1H, 4-H), 7.30–
7.44 (m, 5H, Ar-H). 13C NMR (50 MHz, CDCl3): d = ꢁ 4.90 (q, SiCH3), ꢁ 4.86
(q, SiCH3), 18.8 (s, SiC), 26.3 (q, C(CH3)3), 31.6 (t, C-8), 38.6 (d, C-2), 62.0 (d, C-3),
62.8 (t, C-6), 70.8 (t, C-7), 98.7 (d, C-1), 101.1 (d, C-4), 128.3 (d, C-arom.), 128.5
(d, C-arom.), 129.0 (d, C-arom.), 137.3 (s, C-arom.), 150.7 (s, C-5), 177.5 (s, C-9).
MS (CI, i-Bu), m/z (%): 391 (100) [M+ -H2O], 333 (13), 283 (8), 249 (7), 169 (9),
91 (18), 43 (19).
Anal. Calcd for C21H32O6Si: C, 61.73; H, 7.89. Found: C, 61.90; H, 8.24.
Benzyloxy-6-(tert-butyldimethylsilanyloxymethyl)-2-(2-hydroxyethyl)-4-iodo-
tetrahydropyran-3-ol (11). A solution of the iodolactone 8 (200 mg, 0.4 mmol) in
dry THF (50 mL) was treated under argon at 0°C with lithium aluminum hydride
(LAH) (18 mg, 0.44 mmol). The mixture was allowed to warm to 20°C and stirring
was continued for 1 h (TLC monitoring). The reaction was worked up by addition of
Na2SO4ꢂ10 H2O (200 mg). The mixture was filtered, washed with brine (10 mL), dried
(MgSO4), and the solvent removed under reduced pressure. The crude product was
purified by column chromatography on silica gel (PE/EtOAc 4:1) to yield the diol 11
(178 mg, 86%) as an oil. [a]D + 85.5°, (c 0.97, MeOH). IR (Film): n [cm ꢁ 1] =3420
(OH), 2930 (C H), 2859 (C H), 1455 (C C), 1256 (C O), 1052 (C O).—1H
NMR (200 MHz, CDCl3): d=0.15 (s, 6H, Si(CH3)2), 0.96 (s, 9H, C(CH3)3), 1.71–1.95
(m, 1H, 2-H, 2H, 8-H, 1H, OH), 2.85 (br, 1H, OH), 3.45–3.64 (m, 6H, 3-H, 5-H, 6-H,
9-H), 4.46 (br s, 1H, 4-H), 4.54 (d, J7a,7b =12.0 Hz, 1H, 7a-H), 4.81 (d, J7a,7b = 12.0 Hz,
1H, 7b-H), 4.91 (d, J1,2 = 3.8 Hz, 1H, 1-H), 7.30–7.42 (m, 5H, Ar-H). 13C NMR (50
MHz, CDCl3): d = ꢁ 4.9 (q, SiCH3), ꢁ 4.8 (q, SiCH3), 18.7 (s, SiC), 26.3 (q, C(CH3)3),
31.5 (t, C-8), 34.6 (d, C-2), 36.8 (d, C-4), 60.3 (t, C-9), 65.4 (d, C-3), 68.8 (t, C-6),
70.0 (t, C-7), 73.9 (d, C-5), 99.7 (d, C-1), 128.7 (d, C-arom.), 129.0 (d, C-arom.), 138.0
(s, C-arom.). MS (CI, i-Bu), m/z (%): 523 (4) [M + H + ], 415 (19), 397 (100), 339 (18),
269 (509), 253 (38), 213 (8), 137 (2), 91 (4), 57 (15).
Anal. Calcd for C21H35IO5Si: C, 48.27; H, 6.75. Found: C, 48.81; H, 6.84.
4-Benzyloxy-6-(tert-butyldimethylsilanyloxymethyl)-3a,7a-dihydro-3H,4H-
furo[3,2-c]pyran-2-one (12). A solution of the iodolactone 9 (200 mg, 0.38 mmol) in
dry CH2Cl2 (20 mL) was treated at 20°C with DBU (0.12 mL, 0.76 mmol) and the
mixture was stirred for 10 h (TLC monitoring). Methanol (5 mL), Na2CO3 (63.6 mg,
0.6 mmol), water (5 mL) and HCl (1 mol/L, 0.5 mL) were then added successively

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KROHN, FLORKE, AND GEHLE
440
with stirring. The phases were separated and the organic phase extracted with CH2Cl2
(2 ꢀ 1 mL). The combined organic phases were washed with aqueous NaHCO3 solution
followed by brine (5 mL), dried (MgSO4), and the solvent removed under reduced
pressure. The crude product was purified by column chromatography on silica gel (PE/
EtOAc 4:1) to yield the olefin 12 (117 mg, 78%) as an oil. [a]D +149.5° (c 1.0,
MeOH). IR (Film): n [cm ꢁ 1]= 2940 (C H), 2862 (C H), 1766 (C O, lactone),
1
1476 (C C), 1181 (C C), 1130 (C O), 1094 (C O). H NMR (200 MHz, CDCl3):
d= 0.13 (s, 6H, Si(CH3)2), 0.95 (s, 9H, C(CH3)3), 2.61 (m, 2H, 8-H), 2.86 (m, 1H, 2-
H), 4.05 (s, 2H, 6-H), 4.62 (d, J7a,7b =12.8 Hz, 1H, 7a-H), 4.84 (d, J7a,7b =12.8 Hz, 1H,
7b-H), 4.95 (m, 1H, 3-H), 5.09 (d, J1,2 = 3.7 Hz, 1H, 1-H), 5.35 (d, J4,3 =4.2 Hz, 1H, 4-
H), 7.30–7.42 (m, 5H, Ar-H). 13C NMR (50 MHz, CDCl3): d= ꢁ 5.0 (q, SiCH3), ꢁ 4.9
(q, SiCH3), 18.7 (s, SiC), 26.3 (q, C(CH3)3), 30.8 (t, C-8), 37.5 (d, C-2), 62.4 (t, C-6),
70.7 (t, C-7), 72.3 (d, C-3), 95.4 (d, C-4), 96.2 (d, C-1), 128.2 (d, C-arom.), 128.4 (d,
C-arom.), 129.0 (d, C-arom.), 137.2 (s, C-arom.), 155.0 (s, C-5), 176.5 (s, C-9). MS
(CI, i-Bu), m/z (%): 391 (40) [M +H + ], 333 (3), 283 (3), 254 (11), 176 (45), 133 (5),
91 (6), 57 (100), 43 (19).
Anal. Calcd for C21H30O5Si: C, 64.58; H, 7.74. Found: C, 64.56; H, 7.93.
2-[2-Benzyloxy-6-(tert-butyldimethylsilanyloxymethyl)-3,6-dihydro-2H-pyran-
3-yl]-ethanol (13). A solution of ester 6 (1.80 g, 4.3 mmol) in dry THF (200 mL) was
reduced with LAH (245 mg, 6.5 mmol) as described for 12, to afford the alcohol 13
(1.50 g, 93%) as an oil. [a]D ꢁ 4.2°, (c 2.5, MeOH). IR (Film): n [cm ꢁ 1] = 3410 (OH),
3038 (C H), 2951 (C H), 2919 (C H), 2847 (C H), 1471 (C C), 1362 (C C),
1
1253 (C O), 1093 (C O), 1021 (C
C
H). H NMR (200 MHz, CDCl3): d =0.13
(s, 6H, Si(CH3)2), 0.94 (s, 9H, C(CH3)3), 1.73 (m, 2H, 8-H), 1.96 (br s, 1H, OH), 2.65
(m, 1H, 2-H), 3.60–3.84 (m, 4H, 6-H, 9-H), 4.29 (m, 1H, 5-H), 4.60 (d, J7a,7b =11.7
Hz, 1H, 7a-H), 4.87 (d, J7a,7b = 11.7 Hz, 1H, 7b-H), 5.01 (d, J1,2 = 4.0 Hz, 1H, 1-H), 5.67
(m, 1H, 3-H), 5.82 (m, 1H, 4-H), 7.32–7.40 (m, 5H, Ar-H). 13C NMR (50 MHz,
CDCl3): d= ꢁ 4.8 (q, SiCH3), ꢁ 4.8 (q, SiCH3), 18.8 (s, SiC), 26.3 (q, C(CH3)3), 33.5
(t, C-8), 35.9 (d, C-2), 60.7 (t, C-9), 66.1 (t, C-6), 69.5 (t, C-7), 70.2 (d, C-5), 97.2
(d, C-1), 126.4 (d, C-3), 127.2 (d, C-4), 127.3 (d, C-arom.), 128.1 (d, C-arom.), 128.8
(d, C-arom.), 138.3 (s, C-arom.). MS (EI, 70 eV, 200°C), m/z (%): 327 (4), 269 (11),
253 (58), 213 (28), 195 (26), 143 (13), 125 (58), 121 (58), 91 (100), 65 (12), 41 (18).
Anal. Calcd for C21H34O4Si : C, 66.62; H, 9.05. Found: C, 66.16; H, 9.38.
[2-Benzyloxy-6-(tert-butyldimethylsilanyloxymethyl)-3,6-dihydro-2H-pyran-3-
yl]-acetaldehyde (14). To a suspension of pyridinium chlorochromate (PCC) (522
mg, 2.4 mmol) in dry CH2Cl2 (100 mL) was added under argon a solution of the
alcohol 13 (900 mg, 2.4 mmol) in CH2Cl2 (150 mL). After 2 h (TLC monitoring) the
reaction was filtered through a short column of silica gel (CH2Cl2) to afford the
aldehyde 14 (828 mg, 92%) as an oil. [a]D +4.7° (c 1.05, MeOH). IR (Film): n
[cm ꢁ 1]= 2955 (m, C H), 2924 (m, C H), 2852 (m, C H), 1729 (s, C O), 1471
(HC CH), 1409 (w, C C), 1362 (s, C O), 1254 (s, C O), 1021 (s, C
C
H),
1
834, 778, 736. H NMR (200 MHz, CDCl3): d=0.13 (s, 6H, Si(CH3)2), 0.95 (s, 9H,
C(CH3)3), 2.49 (m, 1H, 8a-H), 2.68 (m, 1H, 8b-H), 3.03 (m, 1H, 2-H), 3.50 (m, 2H, 6-
H), 4.26 (m, 1H, 5-H), 4.56 (d, J7a,7b =12.3 Hz, 1H, 7a-H), 4.84 (d, J7a,7b =12.3 Hz, 1H,
7b-H), 5.10 (d, J1,2 = 4.1 Hz, 1H, 1-H), 5.64 (m, 1H, 3-H), 5.82 (m, 1H, 4-H), 7.30–
7.37 (m, 5H, Ar-H), 9.78 (s, 1H, 9-H). 13C NMR (50 MHz, CDCl3): d= ꢁ 4.9 (q,

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HIGHLY DEOXYGENATED SUGARS. I
441
SiCH3), ꢁ 4.3 (q, SiCH3), 18.8 (s, SiC), 26.3 (q, C(CH3)3), 33.7 (t, C-2), 44.8 (d, C-8),
66.0 (t, C-6), 69.7 (t, C-7), 69.9 (d, C-5), 96.5 (d, C-1), 126.2 (d, C-3), 127.4 (d, C-4),
128.2 (d, C-arom.), 128.3 (d, C-arom.), 128.8 (d, C-arom.), 138.3 (s, C-arom.), 201.6
(d, C-9). MS (EI, 70 eV, 200°C), m/z (%): 355 (12), 327 (4), 269 (18), 253 (100), 237
(23), 213 (32), 195 (26), 143 (13), 125 (54), 121 (77), 91 (62), 65 (10), 41 (16).
Anal. Calcd for C21H32O4Si: C, 66.98; H, 8.57. Found: C, 65.97; H, 8.33.
2-[2-Benzyloxy-6-(tert-butyldimethylsilanyloxymethyl)-3,6-dihydro-2H-pyran-
3-ylmethyl]-2,3-dihydropyran-4-one (16). A solution of the aldehyde 14 (100 mg,
0.27 mmol) in dry CH2Cl2 (20 mL) was treated with dry ZnCl2 (4 mg, 0.03 mmol) and
diene 15 (0.1 mL, 0.6 mmol, 2 equiv.).[12] The mixture was stirred for 8 h (TLC
monitoring) and then quenched by addition of 10% HCl solution (10 mL). After
stirring for 1 h, the phases were separated, the aqueous phase was extracted with
CH2Cl2 (2 ꢀ 3 mL), washed with saturated NaHCO3 solution (20 mL), and dried
(MgSO4). The solvent was removed under reduced pressure and the residue purified by
column chromatography on silica gel (PE/EtOAc 3:1) to afford the oily adduct 16 (49
mg, 77%) and unreacted starting material 14 (37 mg, 63% conversion) as a 1:1 mixture
of stereoisomers. Using MgBr2 (25%, at 60% conversion) or Eu(fod)3 (47% at 66%
conversion) gave the same mixture of isomers. [a]D ꢁ 28.3°, (c 1.1, MeOH). IR (film):
n [cm ꢁ 1]=2955 (C H), 2929 (C H), 2862 (C H), 1683 (C O), 1595 (C C),
1
1409 (C C), 1264 (C C), 1104 (C O), 1041 (C O). H NMR (200 MHz, CDCl3)
(isomeric mixture): d=0.12 (s, 6H, Si(CH3)2), 0.95 (s, 9H, C(CH3)3), 1.73 (m, 2H,
8-H), 2.05 (m, 1H, 9-H), 2.45 (m, 2H, 13-H), 2.73 (m, 1H, 2-H), 3.66 (dd, J6a,5 =5.9
Hz, J6a,6b = 10.1 Hz, 1H, 6a-H), 3.79 (dd, J6b,5 =3.9 Hz, J6a,6b = 10.1 Hz, 1H, 6b-H),
4.28 (m, 1H, 5-H), 4.85 (d, J7a,7b =12.1 Hz, 1H, 7a-H), 4.84 (d, J7a,7b = 12.1 Hz, 1H, 7b-
H), 5.00 (br s, 1H, 1-H), 5.38 (m, 1H, 11-H), 5.65 (m, 1H, 4-H), 5.84 (m, 1H, 3-H),
7.34–7.38 (m, 6H, 10-H, Ar-H). 13C NMR (50 MHz, CDCl3) (major isomer):
d = ꢁ 4.85 (q, SiCH3), ꢁ 4.8 (q, SiCH3), 18.8 (s, SiC), 26.3 (q, C(CH3)3), 34.4 (d, C-2),
35.9 (t, C-8), 42.7 (t, C-13), 66.1 (t, C-6), 69.3 (t, C-7), 69.9 (d, C-9), 70.2 (d, C-5),
65.6 (d, C-1), 107.5 (d, C-11), 126.8 (d, C-4), 127.1 (d, C-3), 127.4 (d, C-arom.), 128.2
(d, C-arom.), 128.5 (d, C-arom.), 128.8 (d, C-arom.), 128.9 (d, C-arom.), 137.9 (s, C-
arom.), 163.3 (d, C-10), 192.7 (s, C-12). MS (EI, 70 eV, 200°C), m/z (%): 444 (1)
[M + ], 387 (2), 369 (1), 279 (7), 209 (8), 157 (6), 129 (6), 105 (12), 91 (100), 74 (30),
65 (10), 57 (8), 28 (18).
Anal. Calcd for C25H3605Si: C, 67.53; H, 8.16. Found: C, 66.43; H, 7.67.
ACKNOWLEDGMENTS
We thank the BMLV (Bundesministerium fu¨r Landwirtschaft und Verbraucherschutz,
project no. 00NR074) for financial support of this work.
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¨
KROHN, FLORKE, AND GEHLE
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HIGHLY DEOXYGENATED SUGARS. I
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18. Full crystallographic data (excluding structure factors) for 9 have been deposited
with the Cambridge Crystallographic Data Centre as supplementary publication
no. CCDC-177341. Copies of the data can be obtained free of charge on appli-
cation to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax: ( +44)1223-336-
033; e-mail: deposit@ccdc.cam.ac.uk).
19. Bruker. SHELXTL. Version 5.1; Bruker AXS Inc.: Madison, Wisconsin, USA, 1998.
Received January 30, 2002
Accepted June 5, 2002