Alkylation of partially protected xylofuranoses and tetritols with (2,2,3,3,4,4,5,5,6,6,7,7,7-tridecafluoroheptyl)-oxirane and the stability of protecting acetal groups towards Lewis acid-type catalyst

Article abstract of DOI:10.1135/cccc20011665

1,2-O-Isopropylidene-3-O-methyl-α-D-xylofuranose (2), 1,2-O-isopropylidene-α-D-xylofuranose (3), 2,4-O-ethylidene-D-erythritol (4) and 1,3-O-ethylidene-D-threitol (5) were alkylated with racemic (2,2,3,3,4,4,5,5,6,6,7,7,7-tridecafluoroheptyl)oxirane (1) using boron trifluoride diethyl etherate as a catalyst. The desired mono- or disubstituted polyfluoroalkyl derivatives 6-11 were isolated only in low to medium yields. The fluoroalkylation was accompanied with disproportional distributions of the protecting acetal/ketal groups and polymerization of saccharides. Therefore the stability of 3, 4, 5, 5-O-acetyl-1,2-O-isopropylidene-α-D-xylofuranose (14) and 1,2-O-isopropylidene-α-D-glucofuranose (15) in the presence of a catalytic amount of boron trifluoride diethyl etherate was investigated in various solvents. A mechanism explaining the effect of the catalyst has been proposed.

Full text of DOI:10.1135/cccc20011665

Alkylation of Xylofuranoses and Tetritols
1665
ALKYLATION OF PARTIALLY PROTECTED XYLOFURANOSES AND
TETRITOLS WITH (2,2,3,3,4,4,5,5,6,6,7,7,7-TRIDECAFLUOROHEPTYL)-
OXIRANE AND THE STABILITY OF PROTECTING ACETAL GROUPS
TOWARDS LEWIS ACID-TYPE CATALYST
a2
a
a3
Karel KEFURTa1,*, Jitka MORAVCOVÁ , Šárka BAMBASOVÁ , Kateřina BUCHALOVÁ ,
a
a
a4
Barbora VYMĚTALÍKOVÁ , Zdeňka KEFURTOVÁ , Jan STANĚK and
b
Oldřich PALETA
a
Department of Chemistry of Natural Compounds, Institute of Chemical Technology, Prague,
166 28Prague 6, Czech Republic; e-mail: karel.kefurt@vscht.cz, jitka.moravcova@vscht.cz,
katerina.buchalova@vscht.cz, jan.stanek@vscht.cz,
Department of Organic Chemistry, Institute of Chemical Technology, Prague, 166 28Prague 6,
Czech Republic; e-mail: oldrich.paleta@vscht.cz
1
2
3
4
b
Received February 2, 2001
Accepted October 26, 2001
1,2-O-Isopropyliden e-3-O-m eth yl-α-D-xylofuran ose (2), 1,2-O-isopropyliden e-α-D-xylofuran ose
(3), 2,4-O-eth yliden e-D-eryth ritol (4) an d 1,3-O-eth yliden e-D-th reitol (5) were alkylated with
racem ic (2,2,3,3,4,4,5,5,6,6,7,7,7-tridecafluoroh eptyl)oxiran e (1) usin g boron trifluoride di-
eth yl eth erate as a catalyst. Th e desired m on o- or disubstituted polyfluoroalkyl derivatives
6–11 were isolated on ly in low to m edium yields. Th e fluoroalkylation was accom pan ied
with disproportion al distribution s of th e protectin g acetal/ketal groups an d polym erization
of sacch arides. Th erefore th e stability of 3, 4, 5, 5-O-acetyl-1,2-O-isopropyliden e-α-D-xylo-
furan ose (14) an d 1,2-O-isopropyliden e-α-D-glucofuran ose (15) in th e presen ce of a catalytic
am oun t of boron trifluoride dieth yl eth erate was in vestigated in various solven ts. A m ech a-
n ism explain in g th e effect of th e catalyst h as been proposed.
Keyw ord s: Carboh ydrates; Fluoroalkylated epoxides; Rin g open in g; Lewis acid catalysis;
Fluoroalkylation s; Fluoroph ilic sugars; Oxygen carriers; Fluorin ated sugars.
Perfluoroalkylated carboh ydrates an d th eir derivatives exh ibit in terestin g
surface, colloidal an d biological properties1. Som e of th em h ave been em -
ployed in m icroem ulsion s used as oxygen carriers for various biom edical
purposes in cludin g blood substitutes2,3, organ preservation un der aerobic
con dition s4, liquid ven tilation or as con trast agen ts for ultrasoun d diagn o-
sis1, etc. Stable fluorocarbon –water em ulsion s are very im portan t for th ese
purposes5. In th is respect, polyh ydroxy com poun ds, e.g. sugars, bearin g a
straigh t polyfluoroalkyl ch ain h ave attracted a rem arkable in terest due to
Collect. Czech. Chem. Commun. (Vol. 66) (2001)
doi:10.1135/cccc20011665

1666
Kefurt et al.:
th eir kn own am ph iph ilicity. Syn th eses an d use of several polyfluoroalkyl
carboh ydrates as em ulsifyin g agen ts h ave been paten ted6,7
.
Various syn th etic strategies h ave been used for perfluoroalkylated surfac-
tan ts with a h ydroph ilic carboh ydrate m oiety in depen den ce on th e reac-
tivity of reaction sites in th e startin g carboh ydrate derivatives1. Som e of th e
am ph iph ilic com poun ds reported in th e literature1 are esters or am ides.
Th ese com poun ds gen erally suffer from lower h ydrolytic stability th an sur-
factan ts con tain in g fluoroalkyl group attach ed to carboh ydrate derivatives
with an eth er lin kage. Recen tly, we h ave developed a con ven ien t m eth od
for fluoroalkylation of h ydroxy com poun ds by th eir reaction with
perfluoroalkylated epoxides8–11
.
In continuation of our research8–11, we present here a study of O-alkylation of
partially protected pentofuranoses and tetritols with (2,2,3,3,4,4,5,5,6,6,7,7,7-
tridecafluoroheptyl)oxirane (1).
RESULTS AND DISCUSSION
Th e easily available 1,2-O-isopropyliden e-3-O-m eth yl-α-D-xylofuran ose12 (2),
1,2-O-isopropyliden e-α-D-xylofuran ose13 (3), 2,4-O-eth yliden e-D-eryth ritol14
(4) an d 1,3-O-eth yliden e-D-th reitol (5) were ch osen as m odel com poun ds
differin g in variable accessibility of th eir un protected h ydroxy groups.
Acetal 5 was prepared from 4,6-O-eth yliden e-D-galactose15 an alogously to
th e m eth od14 described for 4. In con sequen ce of racem ic epoxide 1, m ix-
tures of badly separable diastereoisom ers differin g in th e con figuration on
th e asym m etric carbon of th e attach ed polyfluoroalkyl ch ain can be ex-
pected in products of th e alkylation of th e ch iral substrates 2–5. From th e
poin t of view of th e poten tial application of th e products as co-em ulsifiers
in oxygen carriers, both diastereoisom ers sh ould display bioin ert properties.
Th erefore it is n ot n ecessary to separate th em for in troducin g testin g. Ow-
in g to in stability of polyfluoroalkyls in alkalin e m edium 8, a stron g basic
catalyst of th e m etal alkoxide type16 h ad to be excluded. Hen ce, th e con di-
tion s previously em ployed11 (boron trifluoride dieth yl eth erate as a catalyst,
equim olar ratio of th e reactan ts, diisopropyl eth er as a solven t, tem perature
n ear to th e boil an d dry atm osph ere) were first tested.
In con trast to th e described reaction 11 of 1,2:3,4-di-O-isopropyliden e-
α-D-galactopyran ose, fluoroalkylation s of th e all studied com poun ds 2, 3, 4
an d 5 with 1 proceeded slowly an d, in addition , th ey were com plicated
with th e form ation of several side products as ch ecked by TLC. Th e desired
fluoroalkylated com poun ds 6–11 were obtain ed by a tedious repeated
ch rom atograph y lowerin g th e preparative yield substan tially. Separation
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

Alkylation of Xylofuranoses and Tetritols
1667
of th e diastereoisom ers arisin g from reaction of th e sacch arides with th e
racem ic oxiran e 1 failed. Th us, 1,2-O-isopropyliden e-3-O-m eth yl-5-O-
((RS)-4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluoro-2-h ydroxyn on yl)-α-D-xylofuran ose
(6) was obtain ed from 2 in a yield of 30%. In an attem pt to im prove th e
yield, m olar ratio of th e reactan ts, relative am oun t of th e catalyst, tem pera-
ture, or reaction tim e were varied, but with on ly sm all effect (yield 34%)
R2OCH2
O
O
R2O
R1O
OR1
CH3
O
C6F13
O
O
1
O
R1
CH3
H
R2
H
H
R1
H
R2
H
2
3
6
7
12
14
4
8
9
H
CH2CH(OH)CH2C6F13
1 = R2 = CH2CH(OH)CH2C6F13
>CHCH3
CH3
H
CH2CH(OH)CH2C6F13
CH2CH(OH)CH2C6F13
R
R1, R2
=
17
R1,R2 = >C(CH3)2
H
COCH3
RO
RO
OR2
R3
R1O
O
R2
R3
R3
R3
O
OH
O
CH3
O
O
R1
H
R2
H
R1
H
Bz
H
R2
H
H
OH
R3
OH
OBz
H
5
10
11
19
18a
18b
20a
20b
R
H
H
CH2CH(OH)CH2C6F13
1 = R2 = CH2CH(OH)CH2C6F13
>CHCH3
R
15
16
R1, R2
=
Bz OBz
H
>C(CH3)2
(Table I, en tries 1–5). Th e use of m agn esium perch lorate11 as a catalyst
com pletely failed in th e fluoroalkylation of 2. In O-alkylation of th e diols
3–5, a possibility of th e form ation of m on o- an d disubstituted derivatives
sh ould be con sidered. Notwith stan din g, on ly 1,2-O-isopropyliden e-5-O-
((RS)-4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluoro-2-h ydroxyn on yl)-α-D-xylofuran -
ose (7) was obtain ed from 3 in a very low yield of 6% (Table I, en tries 6,7).
In con trast, th e reaction of acetal 4 with oxiran e 1 afforded 2,4-O-eth yl-
iden e-1-O-((RS)-4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluoro-2-h ydroxyn on yl)-D-
eryth ritol (8) in th e 27% yield on ly if a 1 : 1 m olar ratio of reactan ts was
kept. High er ratio of oxiran e 1 caused th e form ation of disubstituted
2,4-O-eth yliden e-1,3-di-O-((RS)-4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluoro-2-h yd-
roxyn on yl)-D-eryth ritol (9), wh ich was isolated in a low yield in addition to
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

1668
Kefurt et al.:
TABLE I
Alkylation of com poun ds 2–5 with oxiran e 1 catalyzed by BF3·Et2O
Mole ratio
En try Sacch aride
Tem perature Tim e
Yield
%
Product
No.
(m m ol)
°C
h
Sacch aride/1 Sacch aride/BF3·Et2O
1
2
3
4
5
6
2
(0.85)
(1.70)
(2.43)
(1.66)
(2.43)
(2.07)
1/1
1/2
1/0.04
1/0.02
1/0.014
1/0.021
1/0.014
1/0.09
85
80
70
60
50
95
8
9
6
6
26
2
2
2
2
3
25
28
31
34
6
1/1
5
6
1/2
7
6
1/1.5
1/1
8
6
11
7
12a
8
7
8
3
4
(2.07)
(2.50)
1/1
1/0.09
1/0.1
80
95
7
7
3
12a
8
5
1/1.1
11
27
21
12
13
3
4b
17a,c
8
9
4
5
5
(1.89)
(2.63)
(2.53)
1/2.3
1/0.11
1/0.08
1/0.11
95
95
95
11
9
4b
17a,c
10
11
5b
19a
10
11
5b
19a
5
9
10
11
1/1
11
11
4
2.2
27
15
1/2.3
2.6
12
13
13
a
b
c
By-products from th e side activity of catalyst; th e startin g sacch aride recovered; un suc-
cessful to obtain in pure state.
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

Alkylation of Xylofuranoses and Tetritols
1669
th e m on osubstituted product 8 (Table I, en tries 8, 9). Th e reaction of acetal
5 with oxiran e 1 yielded (Table I, en tries 9–11) a m ixture of both 4-O-m on o-
substituted an d 2,4-O-disubstituted derivatives, i.e. 1,3-O-eth yliden e-4-O-
((RS)-4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluoro-2-h ydroxyn on yl)-D-th reitol (10)
an d 1,3-O-eth yliden e-2,4-di-O-((RS)-4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluoro-
2-h ydroxyn on yl)-D-th reitol (11). As sum m arized in Table I, th e con version s
of acetals 4 or 5 were n ot com plete in all experim en ts an d from th e reac-
tion m ixtures of experim en ts with com poun ds 3–5 som e oth er by-products,
h erein after discussed, were isolated (Table I, n otea).
Spectral data an d elem en tal an alyses of all fluorin ated products 6–11 con -
firm ed th e structures suggested. Th e presen ce of th e –(CF2)5CF3 ch ain was
proved by six separated sign als in 19F NMR spectra with th e ch aracteristic
ch em ical sh ift from –78 to –130 ppm , of th e correspon din g in tegral in ten -
1
sity an d m ultiplicity11 (Table II). In H NMR spectra of th e m on osubstituted
derivatives 6–8 an d 10 th e H-1′ an d H-3′ sign als of h ydrogen s on
fluoroalkyl substituen t were observed in th e ran ge of 3.7 to 2.15 ppm an d
th eir duplicity dem on strated a diastereoisom eric com position of all th ese
com poun ds. Th e relative in tegral in ten sities of th e two pairs of distin ctly
separated dd sign als assign ed to H-1′ m eth ylen e proton s correspon ded a 1 : 1
m olar ratio of diastereoisom ers. Th e position s of th e O-fluoroalkyl
substituen t on a sacch aride ch ain were assign ed on th e basis of down field
sh ifts of th e sign als of th e correspon din g H–C–OR n uclei relatively to th eir
ch em ical sh ifts in th e un substituted paren t structure. A com plex ch aracter
1
of th e H NMR spectra of both dialkylated derivative 9 or 11 did n ot allow
TABLE II
19F NMR spectra of com poun ds 6–11. Ch em ical sh ifts of th e sign als of perfluoroh exyl ch ain s
Com poun d
–CH2CF2
3 × CF2
CF2–CF3
CF3
6
7
–113.12
–113.26
–113.25
–113.15
–113.15
–113.27
–122.22
–122.22
–122.31
–122.22
–122.29
–122.33
–123.28
–123.28
–123.37
–123.28
–123.35
–123.40
–124.01
–124.01
–124.08
–124.01
–124.05
–124.11
–126.56
–126.63
–126.65
–126.56
–126.64
–126.67
–81.29
–81.30
–81.33
–81.27
–81.32
–81.36
8
9a
10
11a
a
Sign als of disubstituted derivatives were broad an d poin tless.
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

1670
Kefurt et al.:
an y reason able structural elucidation . In th e 13C NMR APT spectra of 6–11,
th e separated m ultiplets in th e ran ge from 120 to 108 ppm were assign ed to
carbon s of th e perfluoroh exyl ch ain an d a duplicity of som e sign als gave
again an eviden ce of th e n ear 1 : 1 diastereoisom eric com position . Attem pts
to deprotect th e derivative 6 in various trifluoroacetic acid–water m ix-
tures11 was un successful; a rich m ixture of products was always in dicated by
TLC an d separation on a colum n did n ot provide an y pure com poun d.
Low yields of th e expected fluoroalkylated products an d presen ce of som e
oth er com poun ds in reaction m ixtures as n oted in Table I were im puted to
a com plex catalytic activity of BF3·Et2O. As reported17, th is catalyst can be
able to cleave various oxygen bon ds in th e protected sacch arides. Alth ough
cyclic acetal is an excellen t protective group it can possess its own reactiv-
ity17,18 in som e special cases. In gen eral, th e effect of th e Lewis-type of cata-
lyst can be curren tly exploited, inter alia, for th e in troduction , as well as for
th e cleavage of acetal/ketal protectin g cycles19. Owin g to th ese poten tial
reaction s, th e beh avior of 1,2-O-isopropyliden e-α-D-xylofuran ose (3),
2,4-O-ethylidene-D-eryth ritol (4) an d 1,3-O-eth yliden e-D-th reitol (5) in reac-
tion m edia con tain in g a catalytic am oun t of BF3·Et2O was exam in ed un der
various con dition s. Th e com poun ds structurally related to 3, such as
5-O-acetyl-1,2-O-isopropyliden e-α-D-xylofuran ose (14) an d 1,2-O-isopropyl-
iden e-α-D-glucofuran ose (15) were in cluded in th e study for com parison .
Usually, experim en ts were stopped after disappearin g th e TLC-spot of th e
startin g com poun d an d after th at, th e soluble an d solid parts of reaction
m ixture were an alyzed separately.
A solid was precipitated wh en th e solution of 1,2-O-isopropyl-
iden e-α-D-xylofuran ose (3) in diisopropyl eth er was stirred with BF3·Et2O.
The am ount of the precipitate increased with tim e (Table III, entries 1–3), with
an in creasin g ratio of th e catalyst to a substrate (Table III, en tries 3–5) an d
with an in creasin g tem perature of th e reaction (Table III, en tries 6–9),
n am ely. Th e dry precipitate exh ibited m .p. with in a broad in terval. It was
soluble in water, but in soluble in eth an ol, dieth yl eth er, aceton e, ch loro-
form an d ben zen e. 1H an d 13C NMR spectra of it were very com plex as
usual for a m ixture of structurally related com poun ds. MS/ESI spectrum
sh owed groups of ion -lin es differin g orderly by th e m/z value of ≈132
(C5H8O4). Th e first sign ifican t lin e at m/z 345.2 could correspon d to a so-
dium cation ised quasi-m olecular ion of disacch aride 13 [C13H22NaO9]+
(Sch em e 1). Acid h ydrolysis of th e precipitate in com pletely yielded
D-xylose wh ich was iden tified by th e com parison with th e stan dard on TLC
an d HPLC. A m ixture of oligom ers or low polym ers (2–12 pen tose un its of
an un defin ed lin kin g) could be deduced for th e com position of precipitate
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

Alkylation of Xylofuranoses and Tetritols
1671
HO
HO
O
O
H
H O
O
OH
OH
BF3
OH
O
O
O
O
O
F3B
O
3
HO
O
O
O
OH
OH
O
OH
13
O
SCHEME 1
Th e startin g steps of oligom erization of 3
TABLE III
Com position of products of th e reaction of 1,2-O-Isopropyliden e-α-D-xylofuran ose (3; 190 m g,
1 m m ol) in diisopropyl eth er (5 m l, en tries 1–9) or dich lorom eth an e (5 m l, en try 10) in pres-
en ce of BF3·Et2O
Product com position , m g (%)a
Bath
tem perature
°C
Con tact
tim e
h
En try BF3·Et2O
No.
µm ol
3
12
D-xyloseb oligom er
1
2
40
40
40
60
80
40
40
40
40
40
55
55
55
55
55
60
70
80
90
55
1
3
5
5
5
5
5
2
1
5
45 (28)
34 (24)
35 (22)
21 (13)
19 (14)
22 (14)
60 (38)
26 (19)
38 (24)
34 (21)
61 (43)
3
62 (39)
4
21 (13)
11 (7)
22 (14)
108 (66)
153 (94)
120 (72)
134 (82)
164 (100)
165 (100)
126 (72)
c
c
c
5
6
18 (11)
12 (7)
0
5 (3)
5 (3)
0
23 (14)
13 (8)
0
7
8
9
0
0
0
10
9 (5)
21 (12)
20 (11)
a
b
c
Per cen t by th e total weigh t of th e product; D-xylose with a little of oligom er; com -
poun ds 1, 3, an d D-xylose (Σ 10 m g) were n ot separated.
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

1672
Kefurt et al.:
from th e m en tion ed data. Form ation of polym ers in reaction s of various
sacch aride derivatives catalyzed with BF3·Et2O or oth er Lewis acids h as al-
ready been reported20. Mostly, various 1,n-an h ydroaldoses were used for
polym erization aim ed to form ation of polysacch aride ch ain s20a. Poly-
merization of 1,4-anhydro-2,3-O-benzylidene-α-D-ribopyranose or 3,5-anhydro-
1,2-O-isopropyliden e-α-D-xylofuran ose was described21 to yield [1→4]-2,3-
O-ben zyliden e-α-D-ribopyran an an d “[3→5]-1,2-O-isopropyliden e-α-D-xylo-
furan an ”, respectively.
After rem ovin g solven ts,
a
residue from th e liquid part was
ch rom atograph ed yieldin g 1,2:3,5-di-O-isopropyliden e-α-D-xylofuran ose
(12), th e startin g 3, D-xylose an d a m in or portion of oligom ers. An alogous
result was obtain ed usin g dich lorom eth an e as solven t (Table III, en try 10).
On th e oth er h an d, n o ch an ge of th e substrate was observed in diisopropyl
eth er solution s, wh en Mg(ClO4)2 was used as th e catalyst for th e reaction
with 3, or 5-O-acetyl derivative 14 was used as th e substrate.
Regardin g to th e above m en tion ed experien ce with derivative 3, a study
of beh avior of its h om ologue, 1,2-O-isopropyliden e-α-D-glucofuran ose (15),
seem ed to be of in terest. Owin g to a low solubility of 15 in diisopropyl
eth er, th e experim en ts were carried out in dry 1,2-dim eth oxyeth an e at 55,
70 an d 80 °C (Table IV). At 55 °C, com poun d 15 rem ain ed un ch an ged
with in th e experim en t. However, at h igh er tem perature, a com plex m ixture
of soluble an d in soluble products was obtain ed an alogously to th e reaction
TABLE IV
Com position of products of th e reaction of 1,2-O-isopropylidene-α-D-glucofuranose (15; 220 mg,
1.0 m m ol) in 1,2-dim eth oxyeth an e (5 m l) with BF3·Et2O (40 µl) for 5 h
Com position of product, m g (%)a
Bath
En try
No.
tem perature
°C
15
16
D-glucose
oligom er
1
2
3
55
70
80
220 (100)
90 (49)
0
0
0
12 (7)b
10 (6)b
12 (7)c
6 (4)c
44 (24)
54 (32)
76 (45)
a
b
Per cen t by th e total weigh t of th e product; furth er part (ca 25 m g) was con tam in ed by
un defin ed com poun d with RF close to 16, possibly 1,2:3,5-di-O-isopropyliden e-
c
α-D-glucofuran ose; a m ixture of D-glucose an d oligom er (HPLC).
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

Alkylation of Xylofuranoses and Tetritols
1673
of 3. MS of th e solid part sim ilarly sh owed ion lin es orderly differin g by th e
m/z value 162 an d th e gen eral form ula [C15H26NaO11 + (C6H10O5)n]+, for n =
0–6, could be con sidered for th ese ion s. D-Glucose was iden tified in th e acid
h ydrolyzate of th e solid products by HPLC. Colum n ch rom atograph y of th e
soluble part of th e reaction m ixture afforded 1,2:5,6-di-O-isopropyl-
iden e-α-D-glucofuran ose (16), un ch an ged 15, an d D-glucose as prevailin g
com poun ds.
Th e action of BF3·Et2O on 2,4-O-eth yliden e-D-eryth ritol (4) or
1,3-O-eth yliden e-D-th reitol (5) was studied in diisopropyl eth er solution at
70–80 °C. After 5 h , th e solven t was evaporated an d products were sepa-
rated by extraction an d colum n ch rom atograph y. In th e both cases,
1,3:2,4-di-O-eth yliden e derivative 17 or 19, startin g acetal 4 or 5, an d
tetritol 18a or 20a (in th e form of its perben zoate 18b or 20b) were isolated
an d iden tified, respectively. Also som e m in or com poun ds (<5%) sh owin g
TLC spots an d GC-MS spectra close to 17 or 19 were obtain ed from th ese
m ixtures but th eir separation to in dividual com poun ds failed. Accordin g to
ref.22, diastereoisom eric tetraoxadecalin structures can be con sidered for
th ese products. In con trast to th e experim en ts with th e derivative 3 an d 15,
n o polym erization was observed. For th e purpose of iden tification , a stan -
dard sam ple of derivative 17 was prepared by m ean s of reaction of 4 with
paraldeh yde in presen ce of BF3·Et2O.
OH
O
OH
O
HO
HO
O
O
CH3
CH3
H
F3B
BF3
OH
O
HO
HO
O
O
5
CH3
CH3
O
O
OH
HO
BF3
CH3
O
OH
CH3
O
H
O
HO
+
O
OH
OH
O
O
O
H O
CH3
O
CH3
O
20a
19
SCHEME 2
Disproportion ation of th e eth yliden e group in 1,3-O-eth yliden e-D-th reitol (5)
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

1674
Kefurt et al.:
In con clusion , th e tran sform ation s of th e substrates 3, 4, 5 an d 15 in -
duced by BF3·Et2O catalyse proceeded in th e tested solven ts to various de-
gree of con version s an d were tem perature depen den t. Disproportion ation
of th e acetal/ketal groups accordin g to th e Sch em e 2 an d form ation of oli-
gom ers accordin g to Sch em e 1 were foun d in th is work. A furth er in vestiga-
tion is n ecessary for an y m ore precise determ in ation of th e last com poun ds.
All m en tion ed tran sform ation s, quickly proceedin g sim ultan eously with
fluoroalkylation s could cause low yields of th e expected products in th e
fluoroalkylation s of 2–5 with oxiran e 1.
EXPERIMENTAL
Optical rotation s were m easured on a Jasco Model DIP-370 polarim eter an d are given in
10–1 deg cm 2 g–1. Meltin g poin ts were determ in ed on a Kofler block an d are un corrected.
IR spectra were m easured on a FT IR Nicolet 740 spectrom eter, waven um bers are given in
cm –1. NMR spectra were m easured in CDCl3 solution s (tetram eth ylsilan e as an in tern al
stan dard) at 25 °C on a Bruker AM 400 spectrom eter (1H, 400 MHz; 13C, 100.62 MHz; 19F,
376.2 MHz) or on a Bruker Avan ce DRX 500 spectrom eter (1H, 500.1 MHz; 13C, 125.8 MHz;
19F, 470.6 MHz). Ch em ical sh ifts are given in ppm (δ-scale), couplin g con stan ts (J) in Hz.
Th e assign m en t of th e sign als was con firm ed with 1H-1H COSY an d 1H-13C HMQC experi-
m en ts. Th e n uclear Overh auser effect was m easured by h elp of th e double-pulsed-field-
gradien t-spin -ech o (DPFGSE) m eth od.
For th e description of NMR spectra, th e followin g form alism was used: (a) th e
polyfluoroalkyl carbon n um bers are prim ed, e.g. C-1′, C-2′, H-2′, etc.; (b) th e h ydrogen s of
ch ain m eth ylen e groups are distin guish ed by a or b, e.g. H-1′a, H-5b, etc.; (c) th e h ydrogen s
of rin g m eth ylen e groups (in 4, 5, 8, 10) are den oted a or e in dicatin g th e axial or equatorial
position s, respectively, e.g. H-4a, H-1e, etc.; (d) th e separated sign als of th e sam e n uclei in
th e diastereoisom ers are m arked A or B, an d th e com m on , un separated sign als AB, e.g.
H-1′aA, H-5aB, H-3AB, etc.; (e) th e n um bers 5, 6 or 5′, 6′ were assign ed to th e carbon s of th e
eth an e-1,1-diyl group(s), >CH-CH3, e.g. C-5, H-5, C-6′, etc., for description of NMR spectra of
com poun ds 4, 5, 8, 10 an d 17, 19, respectively; (f) in 13C NMR spectra (APT), sign als of car-
bon atom s with 0 or 2 h ydrogen s are in italics.
Mass spectroscopy of th e precipitates arose from 3 an d 15 was realized on API 3000
Perkin –Elm er in strum en t, usin g electrospray ion ization m eth od. MS of th e derivative 17 an d
its isom ers were m easured on th e Hewlett–Packard GC/MS in strum en t 5890 with th e
quadrupol detector 5971A, usin g electron ion ization at 70 eV. Th e APCI spectra of th e deriv-
ative 19 were recorded on an LCQ m ass spectrom eter (Th erm oFin n igan , San Jose). Th e sam -
ple was dissolved in MeOH–water 50 : 50 (10 µg/m l) an d directly in jected via a Valco sam ple
loop (5 µl) in to a stream of th e m obile ph ase, MeOH–water 50 : 50, 0.5 m l/m in .
HPLC: A glass jacket colum n (400 × 4 m m I.D.) with a stron g cation exch an ger OSTION
LG-KS 0802 (Spolek pro ch em ickou a h utn í výrobu a.s., Ústí n ad Labem , Czech Republic) in
Ca2+ form th erm ostated on 70 °C was used. Th e flow rate of deion ized water was m ain -
tain ed at 6 m l/h with an INGOS LCP 5020 pum p (pressure 850 kPa) an d an alyses were m on -
itored with an differen tial refractom etric detector Optilab Multiref 5902 (Tecator, Sweden )
con n ected with a recorder TZ 4200 (Laboratorn í přístroje, Czech Republic).
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

Alkylation of Xylofuranoses and Tetritols
1675
Colum n ch rom atograph y was perform ed on silica gel 60 (Fluka) an d TLC on silica gel ac-
cordin g to Stah l (10–40 µm , Merck, Germ an y). For ch rom atograph ic separation s, th e follow-
in g elutin g system s were used: petroleum eth er–aceton e 8 : 1 (S1), petroleum eth er–aceton e
4 : 1 (S2), ben zen e–eth an ol 10 : 1 (S3), ben zen e–eth an ol 7 : 1 (S4), ben zen e–eth an ol 6 : 1 (S5)
an d eth yl acetate–petroleum eth er 5 : 1 (S6). Th e TLC spots were detected by sprayin g with
a solution of 1% Ce(SO4)2 in 10% H2SO4 an d subsequen t carbon ization . Solution s were con -
cen trated un der reduced pressure at bath tem perature below 40 °C.
Racemic (2,2,3,3,4,4,5,5,6,6,7,7,7-tridecafluoroheptyl)oxirane (1) was prepared by th e de-
scribed m eth od8.
1,2-O-Isopropylidene-3-O-methyl-α-D-xylofuranose12 (2) was prepared as a syrup distillin g at
140 °C/1.3 Pa, [α ]2D5 –64 (c 1.0, CHCl3); ref.23 gives [α ]2D5 –64 (c 1.7, CHCl3). 1H NMR: 5.94 d,
1 H, J = 3.9 (H-1); 4.60 d, 1 H, J = 3.9 (H-2); 4.28 m , 1 H (H-4); 3.90 dd, 1 H, J = 5.3, 11.8
(H-5a); 3.85 dd, 1 H, J = 5.4, 11.8 (H-5b); 3.82 d, 1 H, J = 3.5 (H-3); 3.44 s, 3 H (OCH3); 2.62 bs,
1 H (OH); 1.33, 1.50 2 × s, 2 × 3 H (2 × CH3). 13C NMR: 111.6 (>C(CH3)2); 104.7 (C-1); 85.2
(C-3); 81.6 (C-2); 80.0 (C-4); 60.6 (C-5); 57.7 (OCH3); 26.7, 26.2 (>C(CH3)2).
1,2-O-Isopropylidene-α-D-xylofuranose (3) was prepared accordin g to ref.13. In addition ,
5-O-acetyl-1,2-O-isopropyliden e-α-D-xylofuran ose (14) was obtain ed in 4.2% yield as an arte-
fact arisin g in th e course of preparative ch rom atograph y of 3 by m ean s of tran sesterification
with th e elutin g eth yl acetate, possibly. TLC: RF 0.72 (S6). M.p. 99 °C, [α ]2D0 +22 (c 1, CHCl3).
1H NMR: 5.9 d, 1 H, J(1,2) = 3.5 (H-1); 4.54 d, 1 H (H-2); 4.51 dd, 1 H, J(5,4) = 7.2, J(5,5′) =
11.5 (H-5); 4.25 dd, 1 H, J(4,5′) = 5.3 (H-4); 4.16 dd, 1 H (H-5′); 2.9 bs, 1 H (OH); 2.9 s, 1 H
(H-3); 2.1 s, 3 H (CH3CO); 1.31, 1.49 2 × s, 2 × 3 H (>C(CH3)2). 13C NMR: 171.8 (C=O); 111.8
(>C(CH3)2); 104.7 (C-1); 85.0, 78.2, 74.4 (C-2, C-3, C-4); 61.1 (C-5); 26.8, 26.7, 26.1 (CH3CO,
>C(CH3)2). Literature24 gives m .p. 100–102 °C an d [α ]D20 +25.8 (c 1, CHCl3) for 14. For
C
10H16O6 (232.2) calculated: 51.72% C, 6.94% H; foun d: 51.42% C, 6.77% H.
2,4-O-Ethylidene-D-erythritol14 (4), m .p. 99.5 °C (diethyl ether–petroleum ether), [α ]D25 –52 (c 1.9,
water); ref.14 gives m .p. 99.5 °C an d [α ]D25 –54.7 (c 2, water). 1H NMR: 4.72 q, 1 H, J = 5.1
(H-5); 4.13 dd, 1 H, J = 5.4, 10.8 (H-4e); 3.81–3.89 m , 2 H (H-1a, H-1b); 3.77 dt, 1 H, J = 9.3,
5.4, 5.2 (H-3); 3.41 t, 1 H, J = 10.5, 10.8 (H-4a); 3.12 d, 1 H, J = 5.2 (OH-3); 2.67 t, 1 H, J = 5.4,
5.4 (OH-1); 1.40 d, 3 H, J = 5.1 (3 × H-6). 13C NMR: 98.9 (C-5); 80.7 (C-2); 70.5 (C-4); 62.4
(C-1); 62.1 (C-3); 20.4 (C-6). DPFGSE-NOE: H-5 ↔ H-2; H-5 ↔ H-4a; H-2 ↔ H-4a.
1,3-O-Eth yliden e-D-th reitol (5)
A m ixture of 4,6-O-eth yliden e-D-galactose25 (11 g, 53 m m ol), NaIO4 (23.1 g, 108 m m ol),
NaHCO3 (8.8 g, 105 m m ol) was stirred in water (250 m l) at 20 °C for 2.5 h (TLC, S6: startin g
com poun d, RF 0.46; oxidation product, RF 0.86). After disappearan ce of th e startin g com -
poun d, th e solution was con cen trated in vacuum an d extracted with EtOAc (3 × 50 m l). Or-
gan ic layers were collected, solven t was evaporated an d th e residue was dissolved in
a
m ixture of water (60 m l) an d con cen trated am m on ia (0.5 m l). Saturated solution of BaCl2 in
water was th en added to th e solution an d th e liquid was filtered off. To th e cooled filtrate
con tain in g 2,4-O-eth yliden e-D-th reose, NaBH4 (1.5 g, 40 m m ol) was added with stirrin g dur-
in g 15 m in an d an oth er portion of NaBH4 (0.5 g, 13 m m ol) was added after 2 h (TLC, S6:
th reose acetal, RF 0.86; 5, RF 0.72), an d th e reduction was fin ish ed in 3 h . Th e excess of h y-
dride was decom posed by 1 M HCl (3 m l), pH 9 was th en adjusted with aqueous am m on ia,
th e solution was evaporated an d th e residue extracted with boilin g ch loroform (8 × 200 m l).
Th e crude syrupy acetal 5 (4.05 g, 52%) obtain ed after evaporation of ch loroform was puri-
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

1676
Kefurt et al.:
fied on a silica gel colum n (S5). Recrystallization of th e ch rom atograph ically h om ogen eous
product from aceton e–petroleum eth er gave 2.93 g (37%) of th e acetal 5, m .p. 77 °C, [α ]2D0 –18
(c 1.8, CHCl3); ref.25 gives m .p. 78–80 °C, [α ]D20 –17.6 (c 2.5, CHCl3). IR (CHCl3): 3 574, 3 458,
3 020, 2 943, 2 917, 2 889, 1 454, 1 412, 1 390, 1 370, 1 355. 1H NMR: 4.79 q, 1 H, J = 5.0
(H-5); 4.05 dd, 1 H, J = 1.6, 11.9 (H-1e); 3.86 dd, 1 H, J = 1.0, 11.9 (H-1a); 3.83–3.75 m , 3 H
(H-3, H-4a, H-4b); 3.59 d, 1 H, J = 9.8 (H-2); 3.16 d, 1 H, J = 10.0 (OH-2); 2.68 t, 1 H, J = 5.2
(OH-4); 1.38 d, 3 H, J = 5.0 (3 × H-6). 13C NMR: 99.5 (C-5); 78.9 (C-3); 72.0 (C-1); 64.4 (C-2);
62.8 (C-4); 20.8 (C-6). For C6H12O4 (148.2) calculated: 48.64% C, 8.16% H; foun d: 48.55% C,
8.08% H.
1,3:2,4-Di-O-eth yliden eeryth ritol (17)
A m ixtu re of 2,4-O-eth ylid en e-D-eryth ritol (4; 126 m g, 0.85 m m ol), p arald eh yd e (2 g,
15 m m ol) an d BF3·Et2O (20 µl, 0.4 m m ol) was briefly stirred at room tem perature. After 90 s,
th e reaction was stopped with m eth an ol (2 m l) an d aqueous NaHCO3 (0.5 m l, 10%). Vola-
tile parts were evaporated an d a residue was extracted with dieth yl eth er. After evaporation
of th e solven t, derivative 17 (m .p. 88–89 °C) was obtain ed in th e yield 104 m g (70%) by
sublim ation at 35 °C/1.6 kPa; ref.26 gives m .p. 86–89 °C. 1H NMR: 4.79 q, 2 × 1 H, J = 5.0
(H-5, H-5′); 4.10 dd, 2 × 1 H, J(1e,2) or J(4e,3) = 3.3, J(1e,1a) or J(4e,4a) = 9.9; 3.51–3.63 m ,
4 H (H-1a, H-2, H-3, H-4a); 1.32 d, 2 × 3 H, J(6,5) or J(6′,5′) = 5.0 (H-6, H-6′). 13C NMR: 99.9
(C-5, C-5′); 73.3 (C-2, C-3); 68.3 (C-1, C-4); 20.4 (C-6, C-6′). MS (m/z, rel.%): 173, 159, 130,
115, 100, 87 (100), 79, 69, 61, 59, 45, 43. For C8H14O4 (174.2) calculated: 55.16% C, 8.10%
H; foun d: 55.27% C, 8.29% H.
Reaction of Com poun ds 2–5 with Oxiran e 1. Gen eral Procedure
A ca 10% solution of a sacch aride (2, 3, 4 or 5) in diisopropyl eth er was stirred with oxiran e
1 (1–2 m ole equivalen ts), BF3·Et2O (0.02–0.1 equivalen t) un der gen tle reflux an d th e reac-
tion was m on itored by TLC. Wh en th e startin g substrate disappeared, th e reaction m ixture
was evaporated an d th e residue was separated by flash ch rom atograph y on silica gel.
Ch rom atograph ically n on -un iform fraction s were com bin ed an d repeatedly separated by col-
um n ch rom atograph y. Con dition s an d yields of all experim en ts on alkylation of 2–5 are
sum m arized in Table I.
1,2-O-Isopropylidene-3-O-methyl-5-O-((RS)-4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluoro-2-hydroxynonyl)-
α-D-xylofuranose (6, a m ixture of diastereoisom ers ≈1 : 1) (550 m g, 34%) was obtain ed from
1,2-O-isopropyliden e-3-O-m eth yl-α-D-xylofuran ose (2) (Table I, en try 5) by colum n ch rom ato-
graph y (40 g of silica gel, S1) as a colorless syrup (TLC, S2: RF 0.45). IR (CHCl3): 3 500, 3 022,
2 937, 1 376, 1 365. 1H NMR: 5.93 d, 1 H, J = 3.7 (H-1A); 5.92 d, 1 H, J = 3.7 (H-1B); 4.60 d,
2 H, J = 3.7 (H-2AB); 4.38 m , 2 H (H-4AB); 4.29 m , 2 H (H-2′AB); 3.81 dd, 1 H, J = 5.0, 10.5
(H-5aA); 3.79 dd, 1 H, J = 4.6, 10.4 (H-5aB); 3.75 d, 2 H, J = 3.5 (H-3AB); 3.74 dd, 1 H, J =
4.7, 10.5 (H-5bA); 3.72 dd, 1 H, J = 5.0, 10.4 (H-5bB); 3.65 dd, 1 H, J = 3.5, 9.9 (H-1′aA);
3.61 dd, 1 H, J = 3.7, 9.9 (H-1′aB); 3.52 dd, 1 H, J = 6.6, 9.9 (H-1′bA); 3.48 dd, 1 H, J = 6.6,
9.9 (H-1′bB); 3.405 s, 3 H (OCH3 A); 3.401 s, 3 H (OCH3 B); 2.87 d, 1 H, J = 4.4 (OH-2′A);
2.84 d, 1 H, J = 4.1 (OH-2′B); 2.42–2.20 m , 4 H (H-3′a, H-3′bAB); 1.52, 1.34 2 × s, 2 × 6 H
(>C(CH3)2 AB). 13C NMR: 120.6, 118.1, 116.0, 112.7, 110.7, 108.6 6 × m (C-9′–C-4′AB);
112.4 (>C(CH3)2 AB); 105.7 (C-1AB); 85.0 (C-3AB); 82.1 (C-2AB); 79.7 (C-4AB); 75.5
(C-1′AB); 69.8 (C-5AB); 64.9 (C-2′A); 64.75 (C-2′B); 58.4 (OCH3 AB); 35.4–34.97 m (C-3′AB);
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

Alkylation of Xylofuranoses and Tetritols
1677
27.4, 26.9 (>C(CH3)2 AB). 19F NMR: Table II. For C18H21F13O6 (580.4) calculated: 37.25% C,
3.64% H, 42.56% F; foun d: 37.15% C, 3.51% H, 42.56% F.
1,2-O-Isopropylidene-5-O-((RS)-4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluoro-2-hydroxynonyl)-α-D-xylo-
furanose (7, a m ixture of diastereoisom ers ≈1 : 1) (65 m g, 6%) was obtained from 1,2-O-isopropyl-
iden e-α-D-xylofuran ose (3) (Table I, en try 6) by colum n ch rom atograph y (35 g of silica gel,
S2), m .p. 102–105 °C (dieth yl eth er–petroleum eth er), (TLC, S2: RF 0.32). 1H NMR: 5.96 d, 2 H,
J = 3.3 (H-1AB); 4.52 m , 2 H (H-2AB); 4.33–4.22 m , 6 H (H-3AB, H-4AB, H-2′AB); 3.98–3.90 m ,
4 H (H-5aAB, H-5bAB); 3.68 dd, 1 H, J = 3.2, 10.2 (H-1′aA); 3.65 dd, 1 H, J = 3.2, 10.4
(H-1′a,B); 3.56 dd, 1 H, J = 6.4, 10.3 (H-1′bA); 3.51 dd, 1 H, J = 7.2, 10.1 (H-1′bB); 3.24–3.13 bd,
2 H (OH-2′AB); 2.44–2.15 m , 6 H (H-3′a, H-3′bAB, OH-3AB); 1.50, 1.32 2 × s, 2 × 6 H
(>C(CH3)2 AB). 13C NMR: 121–108 6 × m (C-9′–C-4′AB); 111.9 (>C(CH3)2 AB); 104.8 (C-1AB);
85.3 (C-2AB); 78.4 (C-3A); 78.3 (C-3B); 76.0 (C-4AB); 75.7, 75.4 (C-1′AB); 69.7, 69.5 (C-5AB);
64.4, 64.1 (C-2′AB); 34.6–34.3 m (C-3′AB); 27.4, 26.9 (>C(CH3)2 AB). 19F NMR: Table II. For
C
17H19F13O6 (566.3) calculated: 36.06% C, 3.38% H, 43.61% F; foun d: 36.25% C, 3.53% H,
43.73% F.
2,4-O-Ethylidene-1-O-((RS)-4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluoro-2-hydroxynonyl)-D-erythritol
(8, a m ixture of diastereoisom ers ≈1 : 1) (353 m g, 27%) was obtain ed from 2,4-O-eth yliden e-
D-eryth ritol (4) (Table I, en try 8) by colum n ch rom atograph y (65 g of silica gel, S3) as
colorless syru p (TLC, S3: RF 0.37). IR (CHCl3): 3 447, 3 024, 2 957, 2 870, 1 467, 1 410,
1 365, 1 374, 1 317, 1 243. 1H NMR: 4.69 q, 2 H, J = 4.9 (H-5AB); 4.30 bs, 2 H (H-2′AB);
4.13 dd, 2 H, J = 5.2, 10.7 (H-4eAB); 3.85 dd, 1 H, J = 4.7, 10.5 (H-1aA); 3.84 dd, 1 H, J = 5.7,
10.2 (H-1aB); 3.77 dd, 1 H, J = 3.6, 10.5 (H-1bA); 3.76 m , 2 H (H-3AB); 3.75 dd, 1 H, J = 3.7,
10.2 (H-1bB); 3.67 dd, 1 H, J = 3.2, 10.2 (H-1′aA); 3.65 dd, 1 H, J = 3.1, 10.2 (H-1′aB);
3.55 m , 2 H (H-2AB); 3.54 dd, 1 H, J = 6.3, 10.2 (H-1′bA); 3.49 dd, 1 H, J = 7, 10.2 (H-1′bB);
3.41 t, J = 10.5 (H-4aA); 3.40 t, J = 10.5 (H-4aB); 3.39 bs, 1 H (OH-2′A); 3.25 bs, 2 H
(OH-3AB); 3.245 d, 1 H, J = 3.8 (OH-2′B); 2.43–2.16 m , 4 H (H-3′a, H-3′bAB); 1.34, 1.33 2 ×
s, 2 × 6 H (H-6AB). 13C NMR: 120.6–108.3 6 × m (C-4′–C-9′AB); 99.1 (C-5AB); 79.7 (C-2AB);
75.3 (C-1′A); 74.9 (C-1′B); 71.9 (C-1A); 71.6 (C-1B); 70.5 (C-4AB); 64.4 (C-2′AB); 63.1 (C-3A);
62.9 (C-3B); 34.7–34.3 (C-3′AB); 20.4 (C-6AB). 19F NMR: Table II. For C15H17F13O5 (524.3)
calculated: 34.36% C, 3.27% H, 47.11% F; foun d: 33.93% C, 3.38% H, 47.36% F.
2,4-O-Ethylidene-1,3-di-O-((RS)-4,4,5,5,6,6,7,7,8,8,9,9,9-trideca fluoro-2-hydroxynonyl)-
D-erythritol (9, a m ixture of diastereoisom ers) (50 m g, 3%) was obtain ed from 2,4-O-eth yl-
iden e-D-eryth ritol (4) (Table I, en try 9) as a colorless syrup. 1H NMR: broad un splitted sig-
n als at 4.24, 4.0–3.3, 2.5–2.15, 1.6, 1.34. 13C NMR: broad sign als at 120–108, 99, 80, 76, 75,
71, 69, 68, 65–63, 35–33. 19F NMR: Table II. For C24H22F26O6 (900.4) calculated: 32.02% C,
2.46% H, 54.86% F; foun d: 31.65% C, 2.39% H, 55.22% F.
1,3-O-Ethylidene-4-O-((RS)-4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluoro-2-hydroxynonyl)-D-threitol
(10, a m ixture of diastereoisom ers ≈1 : 1) (50 m g, 4%) was obtain ed from 1,3-O-eth yliden e-
D-th reitol (5) (Table I, en try 10) by colum n ch rom atograph y (70 g of silica gel, S3) as th e
colorless syrup (TLC, S2: RF 0.34). 1H NMR: 5.21, 5.20 2 × q, 2 H, J = 4.7 (H-5AB); 4.29 m ,
4 H (H-1a, H-1eAB); 4.07 m , 1 H (H-2′A); 3.93 m , 1 H (H-2′B); 3.88–3.59 m , 8 H (H-2AB,
H-3AB, H-4aAB, H-4bAB); 3.55 d, 1 H, J = 9.5 (OH-2); 2.81 dd, 1 H, J = 3.0, 12.2 (H-1′aA);
2.73 dd, 1 H, J = 3.0, 12.2 (H-1′aB); 2.30 m , 4 H (H-3′a, H-3′bAB); 2.00 dd, 1 H, J = 12.2, 11.9
(H-1′bA); 1.95 dd, 1 H, J = 12.2, 11.9 (H-1′bB); 1.39 d, 6 H, J = 4.7 (3 × H-6AB). 13C NMR:
120–108 6 × m (C-9′–C-4′AB); 101.8 (C-5AB); 79.4 (C-2AB); 78.5 (C-2′AB); 75.2 (C-4AB);
72.1, 71.7 (C-1′A, C-1′B); 64.4 (C-3AB); 62.5 (C-1AB); 34.6 (C-3′AB); 20.0 (C-6AB). 19F NMR:
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

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Kefurt et al.:
Table II. For C15H17F13O5 (524.3) calculated: 34.36% C, 3.27% H, 47.11% F; foun d: 34.63% C,
3.45% H, 47.39% F.
1,3-O-Ethylidene-2,4-di-O-((RS)-4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluoro-2-hydroxynonyl)-D-threitol
(11, a m ixture of diastereoisom ers) (270 m g, 12%) was obtain ed from 1,3-O-eth yliden e-
D-th reitol (5) (Table I, en try 11) by colum n ch rom atograph y (80 g of silica gel, S3) as a color-
less syrup (TLC, S2: RF 0.36). 1H NMR: 5.21, 5.20 2 × q, 2 H, J = 4.7 (H-5AB); broad
un splitted sign als at 4.28, 4.23, 3.71–3.51, 2.9, 2.28, 1.39 d, 6 H, J = 4.7 (H-6AB). 13C NMR:
120–108 (sign als separated with difficulty from n oise), 101.8, 90.9, 78.1, 75.4, 74.9, 72.0,
71.8, 71.7, 64.3, 34.6, 29.7, 19.9. 19F NMR: Table II. For C24H22F13O6 (900.4) calculated:
32.02% C, 2.71% H, 54.86% F; foun d: 31.77% C, 2.71% H, 55.14% F.
Th e Stability of 1,2-O-Isopropyliden e-α-D-xylofuran ose (3)
an d 1,2-O-Isopropyliden e-α-D-glukofuran ose (15) un der th e Attack of BF3·Et2O.
Gen eral Procedure
A solution of 3 or 15 (1 m m ol) in appropriate solven t (Tables III an d IV) was stirred with
40–80 µm ol of BF3·Et2O at th e selected tem perature with absen ce of m oisture. After desig-
n ated tim e, th e precipitated an d liquid parts were separated by filtration . Th e precipitate was
wash ed with th e used solven t (2 × 5 m l) an d with ch loroform (2 × 5 m l), dried in vacuum
an d an alyzed by h elp of spectral m easurem en t, HPLC an d elem en tal an alysis. Acid h ydroly-
sis of precipitate from 3 or 15 (50–70 m g) proceeded in water (2 m l) by stirrin g with Dowex
50W (H+) (1 m l) or in HCl (2 m l, 1 M water solution ) at room tem perature, with HPLC an al-
ysis of th e h ydrolyzate. Th e liquid part (an origin al filtrate com bin ed with th e wash in g sol-
ven ts) was evaporated an d th e residue was ch rom atograph ed on silica gel, usin g stepwise
elution with eth yl acetate–petroleum eth er 1 : 1 → eth yl acetate → eth an ol for separation of
m ixture from 3 an d ch loroform –m eth an ol 20 : 1 → ch loroform –m eth an ol 10 : 1 → eth an ol
for separation of m ixture from 15. Th e separated com poun ds (Tables III an d IV) were iden ti-
fied by com parison with stan dards by m ean s of th e NMR spectroscopy or HPLC.
Th e precipitate from 3: M.p. 165–195 °C. 1H NMR: con tin uous spectrum with broad peaks
at δ-values: 5.90, 5.05, 4.60, 4.50, 4.08, 3.70, 3.50, 3.38, 1.39, 1.30, 1.26. 13C NMR: 103.7,
99.1, 97.8, 92.4, 79.5, 76.7, 74.7, 73.2, 72.4, 69.7, 65.7, 62.1, 26.1. MS (th e m ost abun dan t
ion s): 345.2, 477.3, 609.3, 741.4, 873.5, 1 005.6, 1 137.6, 1 269.7, 1 401.8, 1 533.8, 1 665.9,
1 798.0, 1 930.0, correspon din g with quasi-m olecular sodium cation ized ion s of gen eral for-
m ula [C13H22NaO9 + (C5H8O4)n]+ for n = 0–12. HPLC: 5 peaks with th e capacity factors k′ =
0.0 (90.6%), 0.05 (2.5%), 0.09 (2.0%), 0.14 (1.7%), 0.44 (3.2%). HPLC of th e h ydrolyzate:
D-xylose (capacity factor k′ = 0.44). Elem en tal an alysis: Foun d: 44.83% C, 6.80% H.
Th e precipitate from 15: M.p. 120–130 °C. MS (th e m ost abun dan t ion s): 405.2, 567.3,
729.4, 891.5, 1 053.6, 1 215.7, 1 377.7, correspon din g with quasi-m olecular sodium
cation ized ion s of gen eral form ula [C15H26NaO11 + (C6H10O5)n]+, for n = 0–6. HPLC: 5 peaks
with th e capacity factors k′ = 0.0 (33%), 0.09 (16%), 0.16 (16%), 0.21 (7%), 0.35 (28%).
HPLC of th e h ydrolyzate: D-glukose (capacity factor k′ = 0.35). Elem en tal an alysis: Foun d:
42.06% C, 6.13% H.
Results of experim en ts are sum m arized in Tables III an d IV.
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Alkylation of Xylofuranoses and Tetritols
1679
Beh avior of 2,4-O-Eth yliden e-D-eryth ritol (4) in Presen ce of BF3·Et2O
A solution of derivative 4 (1 020 m g, 6.85 m m ol) in diisopropyl eth er (30 m l) was stirred
with BF3·Et2O (40 µl, 0.3 m m ol) at th e bath tem perature 80 °C. After 5 h , th e reaction
m ixture was evaporated an d th e residue was extracted with CH2Cl2 (8 × 50 m l). From th e col-
um n ch rom atograph y of th e extract, 1,3:2,4-di-O-eth yliden eeryth ritol (17; 240 m g, 1.4 m m ol,
20%) an d 2,4-O-eth yliden e-D-eryth ritol (4; 490 m g, 48%) were obtain ed. Spectral an d oth er
data of th e isolated com poun ds 17 an d 4 were in accordan ce with data of th e stan dard sam -
ples.
Th e residue n on -extractable with CH2Cl2 (a crude eryth ritol 18a, 202 m g) was solved in
pyridin e (10 m l) an d esterified with ben zoyl ch loride (1 m l) to 1,2,3,4-tetra-O-benzoyl
erythritol (18b) in th e yield 780 m g (1.45 m m ol, 21% to 4). After recrystallization from
eth an ol it exh ibited m .p. 190 °C; ref.27 gives m .p. 188–189 °C. 1H NMR: 8.0 dd, 8 H; 7.55 m ,
4 H; 7.42 q, 8 H (arom .); 5.97 m , 2 H (H-2, H-3); 4.89 dd, 2 H, J = 2.4, 12.2 (H-1, H-4); 4.65 dd,
2 H, J = 5.2, 12.2 (H-1′, H-4′). 13C NMR: 166.0, 165.4 (C=O); 133.4, 133.2, 129.8, 129.7,
129.4, 129.3, 128.5, 128.4 (arom .); 70.1 (C-2, C-3); 62.7 (C-1, C-4). For C32H26O8 (538.6) cal-
culated: 71.37% C, 4.87% H; foun d: 71.47% C, 5.01% H.
Beh avior of 1,3-O-Eth yliden e-D-th reitol (5) in Presen ce of BF3·Et2O
A solution of derivative 5 (136 m g, 0.91 m m ol) in diisopropyl eth er (5 m l) was stirred with
BF3·Et2O (5 µl, 40 µm ol) at th e bath tem perature 70 °C. After 5 h , reaction m ixture was
evaporated an d th e residue was treated as in th e preceden t experim en t. Th e com bin ed di-
ch lorom eth an e parts were evaporated an d th e residue (122 m g) was ch rom atograph ed on sil-
ica gel (15 g) colum n . 1,3:2,4-Di-O-ethylidene-D-threitol (19; 41 m g, 0.24 m m ol) an d th e
startin g 5 (64 m g, 0.43 m m ol) were eluted with ben zen e–eth an ol 50 : 1 an d toluen e–eth an ol
50 : 1, respectively. In separable com poun ds with RF close to 19 foun d in som e m in or frac-
tion s (Σ ≈12 m g) are as isom ers of th e 19 con sidered22. Th e derivative 19 sh owed m .p.
123–124 °C, [α ]2D0 –39 (c 1, CHCl3). 1H NMR: 4.77 q, 2 × 1 H, J = 5.2 (H-5, H-5′); 4.11 d, 2 × 1 H,
J = 12.6, 1 (H-1e, H-4e); 3.84 dd, 2 × 1 H (H-1a, H-4a); 3.56 m , 2 × 1 H (H-2, H-3); 1.41 d, 2 ×
3 H (H-6, H-6′). 13C NMR: 98.8 (C-5, C-5′); 69.54 (C-1, C-4); 69.35 (C-2, C-3); 21.0 (C-6,
C-6′). NMR data correspon ded to th e described22 on es of th e racem ic form . MS: 175 (M + 1)+.
For C8H14O4 (174.2) calculated: 55.16% C, 8.10% H; foun d: 55.04% C, 8.21% H.
Th e part in soluble in CH2Cl2, wh ich was assum ed to be D-th reitol (20a; 26 m g, 0.21 m m ol)
was solved in pyridin e (5 m l) an d stirred with ben zoyl ch loride (150 µl, 1.3 m m ol) at room
tem perature for 12 h (TLC, S3: startin g com poun d, RF 0.0; product, RF 0.86). After a usual
treatm en t, th e product was recrystallized from eth an ol (0.7 m l). 1,2,3,4-Tetra-
O-benzoyl-D-threitol (20b) was obtain ed in th e yield 101 m g (88%), m .p. 96–97 °C, [α ]2D5 –6 (c 1,
CHCl3); ref.28 gives m .p. 97 °C, [α ]2D5 –4.2 (c 1, CHCl3). 1H NMR: 8.02 dd, 8 H; 7.54 m , 4 H;
7.41 q, 8 H (arom .); 5.99 m , 2 H (H-2, H-3); 4.78 dd, 2 H, J = 3.8, 12.0 (H-1, H-4); 4.68 dd, 2 H,
J = 5.8, 12.0 (H-1′, H-4′). 13C NMR: 166.0, 165.6 (C=O); 133.5, 133.3, 129.9, 129.8, 129.4,
129.3, 128.5, 128.4 (arom .); 70.1 (C-2, C-3); 62.8 (C-1, C-4). For C32H26O8 (538.6) calcu-
lated: 71.37% C, 4.87% H; foun d: 71.13% C, 4.69% H.
The authors are indebted to colleagues from several departments of the Central laboratories, Insti-
tute of Chemical Technology, Prague for careful spectral measurements and elemental analyses. The
NMR NOE spectra were kindly measured by Dr H. Dvořáková. For MS measurments we thank Dr L.
Kubelka (Léčiva a.s., Prague), Dr P. Šimek (Institute of Entomology, Academy of Sciences of the Czech
Collect. Czech. Chem. Commun. (Vol. 66) (2001)

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Kefurt et al.:
Republic) and Dr P. Zachař (Department of Analytical Chemistry, Institute of Chemical Technology,
Prague). This research was partly supported by the Grant Agency of the Czech Republic (grant No.
203/98/1174) and also by the Ministry of Education, Youth and Sports of the Czech Republic (project
No. 223300006).
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