Synthesis and liquid crystalline properties of mono-, di- and tri-O-alkyl pentaerythritol derivatives bearing tri-, di- or monogalactosyl heads: The effects of curvature of molecular packing on mesophase formation

FULL PAPER

DOI: 10.1002/chem.200601702

Synthesis and Liquid Crystalline Properties of Mono-, Di- and Tri-O-alkyl

Pentaerythritol Derivatives Bearing Tri-, Di- or Monogalactosyl Heads:

The Effects of Curvature of Molecular Packing on Mesophase Formation

Fabienne Dumoulin,^[a]Dominique Lafont,^[a]Thai-LÞ Huynh,^[a]Paul Boullanger,*^[a]

Grahame Mackenzie,^[b]Jon J. West,^[b]and John W. Goodby*^[c]

Abstract: Self-organisation and self-as-

sembly are critical to the stability of

synthetic and biological membranes. Of

particular importance is consideration

of the packing arrangements of the var-

ious molecular species. Both phospho-

and glycolipids can pack in ways in

which curvature can be introduced into

self-organised or self-assembled sys-

tems. For instance, it is known that the

degree of curvature can affect the

structures of any condensed phases

that are formed. In this article we

report on a systematic study in which

we have varied the shapes of glycoli-

pids and examined the condensed

phases that they form. In doing so, we

have also unified the shape dependen-

cy of lyotropic liquid crystals with

those of thermotropic liquid crystals. In

order to undertake this systematic

study a range of different pentaerythri-

tol derivatives was synthesized, which

covers combinations of one to three

alkyl chains of different lengths

(6,7,9,10,11,12,14,16 carbon atoms)and

three to one galactosyl heads. Mono-

and di-O-galactosyl derivatives were

prepared directly by glycosylation of

the corresponding alcohols using

2,3,4,6-tetra-O-benzoyl or acetyl-a-d-

galactopyranosyl trichloroacetimidate

or bromide as the donors; the tri-O-

galactosyl derivatives were synthesized

from O-alkyl-O-benzyl di-O-galactosyl

pentaerythritol intermediates, followed

by de-O-benzylation and glycosylation

steps. All of the fully deprotected prod-

ucts were obtained by standard meth-

ods, and their self-organising and self-

assembling properties examined.

Keywords: glycosylation · lipids ·

liquid crystals · pentaerythritol

Introduction

volve the extremes of specific recognition processes to me-

chanical/pressure self-regulation. In terms of specific recog-

nition processes, interactions between the carbohydrate

parts of glycoconjugates and proteins are essential to cell

function. In such interactions the terminal carbohydrate

head groups are generally responsible for binding to ligands

(e.g., proteins).^[1–3]Although important in protein–carbohy-

drate recognition, this interaction appears to be relatively

weak when examined experimentally. It has been shown

that proteins have a greater affinity for glycolipids bearing

multivalent carbohydrate ligands than for corresponding

monovalent glycolipids.^[4,5]This phenomenon is known as

the “cluster glycoside effect”.

Over the last ten years, the synthesis and study of various

novel neoglycoconjugates has increased in respect to the

demand for substances with higher affinities and increased

specificity.^[6,7]In particular, attention has been given to sialic

acid and sialyloligosaccharides, together with mannosides

and galactosides since such carbohydrate residues represent

immuno-dominant structural elements.

Biological membranes contain components of varying com-

plexity and functionality; for example, functionality may in-

[a] Dr. F. Dumoulin, Dr. D. Lafont, T.-L. Huynh, Dr. P. Boullanger

UniversitØ de Lyon, Laboratoire de Chimie Organique II

UnitØ Mixte de Recherche CNRS 5181

UniversitØ Lyon 1, Chimie Physique Electronique de Lyon

43 Bd du 11 Novembre 1918, 69622 Villeurbanne (France)

Fax : (+33)478-898-914

E-mail: paul.boullanger@univ-lyon1.fr

[b] Prof. G. Mackenzie, Dr. J. J. West

The Department of Chemistry, The University of Hull

Hull, HU67RX (UK)

[c] Prof. J. W. Goodby

Department of Chemistry, The University of York

Heslington, York, YO105DD (UK)

Fax : (+44)1904-432-516

E-mail: jwg500@york.ac.uk

Supporting information for this article is available on the WWW

under http://www.chemeurj.org/ or from the author.

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Other substances which are able to mimic glycolipid as-

semblies at cell surfaces include synthetically hydrophobised

carbohydrates, because they are able to spontaneously self-

organize in water, either in the presence or absence of other

lipids. Carbohydrate recognition of such organized systems

(mono- or bilayers)is somewhat different to recognition in

isotropic media. Furthermore, the conformation and motion

of the carbohydrate moiety of glycolipids embedded at in-

terfaces are strongly affected by the nature of the lipid

anchor and that of the surrounding lipid components.

Through various related studies, it has been possible to ra-

tionalize and model the structural self-organization of am-

phiphilic carbohydrates by considering the structural geome-

tries and functional features of the individual molecules. For

example, the formation of micelles, liquid crystals, monolay-

ers, or vesicles has been found to be dependent on the

cross-sectional and surface area of the polar head relative to

the length and volume of the apolar tail.^[8]

The relationship between the cross-sectional areas and

volumes of the head groups and tails is connected to the in-

duction of curvature upon packing of the molecules togeth-

er, which in turn determines the nature and structure of any

self-organised mesophase that is formed. In biological cell

membranes the effects of curvature are tightly controlled by

integral and surface proteins which selectively introduce cer-

tain lipids into the outer membrane leaflets.^[9–11]Further-

more, there are some indications that by affecting the

degree of curvature in membranes cubic phases can be in-

troduced locally. The incorporation of such phases effective-

ly opens up a passageway into the inner parts of the cell.^[12]

It appears that the selectivity of interactions and the bulk

organisation of lipid systems in the liquid crystal environ-

ment are of considerable importance to cell function. Thus

as a part of our work devoted understanding these process-

es, particularly in neoglycolipids,^[13–16]we now report the

preparation and systematic study of the liquid crystal prop-

erties of a range of pentaerythritol derivatives which are

substituted by one to three alkyl chains of different lengths,

I, II and III, with the remaining hydroxyl positions being

galactosylated in each case.

Figure 1. Effects of curvature of molecular packing on mesophase forma-

tion in lyotropic systems, and potentially in thermotropic liquid crystals.

posed to examine the variation of phase type as a function

of curvature in dry, thermotropic systems.

In addition to systematically examining the self-organising

properties of glycolipids as a function of the number of gal-

actose units in the head groups, we also sought to investigate

the effects of curvature associated with the packing of the

molecules on mesophase formation. It is generally known

for lyotropic liquid crystal phases that, as the “curvature” is

varied from negative to positive, it can be possible for a pas-

sage through all of the mesophases, that is, from cubic–hex-

agonal–cubic–lamellar–cubic–hexagonal–cubic phases (see

Figure 1). In some cases, however, it is possible to miss out

certain of the phases in the sequence, which can be the case

for galactosides. However, for thermotropic liquid crystal

phases, the effects of curvature of packing on mesophase

formation have not been examined fully. Indeed the phases

formed by mesogens of unconventional structure (phasmidic

Results

Synthetic rationale: Pentaerythritol has been used in the last

ten years as a core component for the syntheses of glycoside

clusters of glycolipids. In most cases a spacer has been intro-

duced between the hydroxyl(s)group(s)of the pentaerythri-

tol core and the glycosyl moieties. For example, Hanessian

et al. prepared clustered a-d-GalNAc-Ser (Tn)and b-d-Gal-

(1!3)-a-d-GalNAc-Ser antigenic motifs, by condensation of

the corresponding glycopeptides with alkyl tris(aminoethyl)

pentaerythritol.^[27]A similar pentaerythritol derivative was

used to obtain clusters of a-d-Gal-(1!3)-b-d-Gal glycosides

of quinic acid.^[28]Recently, glycotope biosteres bearing b-d-

galactose moieties have been synthesized by the Sonoga-

shira reaction of tetra-O-iodobenzyl pentaerythritol and 2-

propinyl galactosides.^[29]Two other routes to mannoside

and banana materials, dendrimers, Janus materials etc.^[17–26]

are exciting topics of current interest. Thus we also pro-

)

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O-Alkyl Pentaerythritol–Galactose Derivatives

FULL PAPER

clusters using pentaerythritol as scaffold have been de-

scribed by Lindhorst et al.:^[30]in the first, pentaerythritol tet-

rabromide was etherified by 2-hydroxyethyl mannosides; in

the second, hydroboration of tetra-O-allyl pentaerythritol

and subsequent mannosylation of the tetraol afforded the

expected tetramannoside which was tested as an inhibitor of

mannose-specific bacterial adhesion.

In the synthesis of some highly hydrophobic Lewis X gly-

colipids,^[31]pentaerythritol was first condensed with triethy-

lene glycol. The hydroxyl groups of the latter were then

etherified by phytyl chains and the subsequent product was

glycosylated with Lewis X donors. There are only a few ex-

amples in the literature of direct glycosylation of partly pro-

tected pentaerythritols. One such example was conducted in

our laboratory, which involved glycosylation of di-O-hexa-

decyl pentaerythritol to give, the gemini glycoside, bis(N-

acetyl-b-d-glucosaminyl)glycosides which were used to study

the interfacial behaviour.^[32]More recently, M. Schmidt

et al.^[33]described the synthesis of mannose clusters having a

pentaerythritol core, in which the mannosyl residues were

either attached directly to the pentaerythritol moiety or sep-

arated from the later by oligoethylene spacers of varying

lengths.

The first part of our synthetic work was the preparation

of the alcohol acceptors as depicted in Scheme 1. The tri-O-

alkyl pentaerythritols 2a–h (chain lengths n = 6, 7, 9–12, 14

and 16)were obtained by direct treatment of pentaerythritol

(1)with an excess of alkyl bromide under phase transfer

conditions, in the presence of 50% aqueous sodium hydrox-

ide and tetrabutylammonium bromide, as described in the

literature for tri-O-heptyl pentaerythritol.^[34]The low yields

were due to the simultaneous formation of mono-, di- and

tetra-O-alkyl derivatives. The di-O-alkyl pentaerythritols

5a,f–h were obtained from O-benzylidene pentaerythritol

3,^[35]by alkylation under similar conditions to afford 4a,f–h

and subsequent cleavage of the benzylidene group, in each

case, by hydrogen transfer (cyclohexene, palladium hydrox-

ide, ethanol, 808C). Treatment of the O-benzylidene pen-

taerythritol 3 with dibutyltin oxide in methanol, followed by

reaction with alkyl bromide in the presence of caesium fluo-

ride, afforded the mono-O-alkyl derivatives 6 f,h, which

were always contaminated by 5–10% of the alkyl alcohol.

Reductive cleavage of the benzylidene group gave the O-

alkyl-O-benzyl pentaerythritols 7 f,h in 40% yield over the

two steps. Compounds 6h and 7h have been reported re-

cently in the literature.^[36]

Scheme 1. Derivatisation of pentaerythritol.

reacted with the alcohol 5h (cat. TMSOTf, CH₂Cl₂, 08C)to

afford the expected di-O-galactoside 13h in 56% yield.

The per-O-benzoyl galactosides 11a,f–h were obtained

under the same conditions from donor 8 and acceptors 2a,f–

h (72–76%). The per-O-acetyl glycosides 12a,f–h were also

prepared in good yields (73–79%)from donor 9 (I₂, 2,3-di-

chloro-5,6-dicyano-1,4-benzoquinone, MeCN)and acceptors

2a,f–h, using a method described in 1996 by Fields and co-

workers.^[40]In contrast, lower yields of galactosides 12a, f–h

(35–53%)were obtained from 2a,f–h using per-O-acetyl

imidate 10. Alternative conditions of Hg(CN)₂, HgBr₂in

CH₂Cl₂were employed to synthesize 12b–e from donor 9

and acceptors 2b–e in reasonable yields (53–66%).

The di-O-alkyl di-O-galactoside derivatives 13a,f–h were

synthesized from imidate 8 and the corresponding diols

5a,f–h in acceptable yields (45 to 72%)using TMSOTf. Al-

ternatively, compound 14g was prepared in 40% yield from

5g and bromide 9 using Fields’ conditions.^[27,40]For purifica-

tion and identification purposes, the per-O-acetyl galacto-

sides 14a,f–h were prepared from their benzoyl counterparts

13a,f–h by Zemplen de-O-benzoylation and re-O-acetyla-

tion.

The trigalactosylation of mono O-alkylpentaerythritol in-

termediates to compounds 17 f,h was unsuccessful, due to

difficulties of separation from the mono- and di-O-glycosyl

by-products. Therefore, 17 f,h were prepared via two glyco-

sylation steps. In the first, acceptors 7 f,h were glycosylated

with imidate 8. The di-O-galactosyl derivatives 15 f,h thus

obtained (68–72%)were then transformed by de- O-benzy-

lation into acceptors 16 f,h (92%), respectively. The latter

were subsequently glycosylated again under the same condi-

tions affording the O-alkyl tris(per-O-benzoyl galactosyl)

pentaerythritols 17 f,h. For purification and identification

purposes, de-O-benzoylation was achieved under ZemplØn

conditions (catalytic amount of CH₃ONa in methanol), fol-

Galactosylation reactions were performed using 2,3,4,6-

tetra-O-benzoyl-a-d-galactopyranosyl trichloroacetimidate

(8),^[14,37]2,3,4,6-tetra-O-acetyl-a-d-galactopyranosyl bromide

(9)^[38]or 2,3,4,6-tetra-O-acetyl-a-d-galactopyranosyl trichlor-

oacetimidate (10)^[39]as glycosyl donors (Scheme 2). In a first

attempt, we studied the galactosylation of diol 5h with the

donors 9 [Hg(CN)₂, HgO, CaSO₄, CH₂Cl₂] and 10 [cat. tri-

methylsilyl trifluoromethanesulfonate (TMSOTf), CH₂Cl₂,

ꢀ208C]. The yields remained low due to the formation of

mixtures of mono- and di-O-galactosyl products, which both

showed very similar behaviour by TLC. Donor 8 was then

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P. Boullanger, J. W. Goodby et al.

Scheme 2. Formation of series I, II and III.

lowed by re-O-acylation to obtain the derivatives 18 f,h in

good yields.

The fully deprotected derivatives 19a–h, 20a,f–h and

21 f,h were prepared in high yields by Zemplen de-O-acety-

lation of the peracetylated derivatives 12a–h, 14a,f–h and

18 f,h, respectively.

was possible to determine melting and clearing points by

differential scanning calorimetry, determination of the asso-

ciated enthalpies was not possible due to decomposition of

the compounds in aluminium pans. The microscope data for

the three homologous series of pentaerythritol derivatives

taken by thermal polarized microscopy is compiled in

Table 1.

Transition temperatures: Phase identifications and determi-

nation of phase transition temperatures were carried out,

concomitantly, by thermal polarized light microscopy (see

Experimental Section for details). Differential scanning cal-

orimetry was also used to confirm the phase transition tem-

peratures determined by optical microscopy. Although it

O-b-d-Galactopyranosyl-tri-O-alkyl pentaerythritols (I):

All materials except 19a, the hexyl homologue, exhibited

normal melting points determined by optical microscopy.

Compound 19a, however, existed in its mesophase or soft

crystal state at room temperature, and thus no melting point

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O-Alkyl Pentaerythritol–Galactose Derivatives

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Table 1. Transition temperatures T [8C] for series I–III.

I

Cpd.

n

Crystal

T

Columnar

T

Cubic

T

Isotropic

liquid

[a]

*

19a

19b

19c

19d

19e

19 f

19g

19h

6

7

9

10

11

12

14

16

–

62.3

72.1

59.4

53.3

38.3

32.0)–

–

*

44.0

36.0

37.0

30.0

37.5

52.7

58.2

82.3

76.2

63.8

43.4

A

–

II

Cpd.

n

Crystal

T

Smectic A*

T

Isotropic

liquid

[a]

*

Figure 2. Transition from discontinuous cubic phase to columnar phase

for O-b-d-galactopyranosyl-tri-O-undecanyl pentaerythritol (C₁₁19b)

20a

20 f

20g

20h

6

–

156.2

203.1

202.2

12

14

16

53.3

46.9

41.7

A

III

Cpd.

n

Crystal

T

Cubic

T

Isotropic

liquid

*

21 f

21h

12

16

91.6

150.0

204.0

>200.0 decomp

[a] Material in its condensed or amorphous phase at room temperature.

was recorded. Compounds 19g and 19h were found to be

non-mesogenic.

A number of O-b-d-galactopyranosyl-tri-O-alkyl pentaer-

ythritols (C₇19b to C₁₁19e)were found to exhibit two

liquid crystal phases; the columnar and cubic phases. The

columnar phase gave textures typical of the hexagonal

phase, whereas the cubic phase appeared optically extinct.

The transition from the cubic phase to the isotropic liquid

was observed via the insertion of a phase plate into the mi-

croscope above the objective and observing the Becker line

between the two phases. The cooling cycle transition from

the cubic phase to the columnar phase for compound 19e

(C₁₁)is shown in the photomicrograph in Figure 2. Fans typi-

cal of the hexagonal phase are formed, they have no ellipti-

cal or hyperbolic lines of optical discontinuity as found for

lamellar phases, and indeed lines associated with rectilinear

defects were observed.

The transition temperatures as a function of chain length

are shown in Figure 3 for compounds 19a–f. The graphical

representation shows that all except for 19 f exhibit enantio-

tropic liquid crystal mesophases. Elongation of the three

alkoxy chains attached to the pentaerythritol core results in

a strong reduction of the transition temperatures. Converse-

ly, the melting points first fall and then increase, thereby

rendering the longer chain length homologues as being non-

mesogenic. The phase range for the columnar mesophase is

greatest for the heptyl compound (28.18C), but for longer

chain length members the stability of this phases decreases

markedly with increasing chain length. Conversely, the

nonyl homologue, 19c, is found to display the most stable

cubic mesophase (16.88C). The compounds either side, 19b

and d, have a considerably reduced cubic phase range in

Figure 3. Comparison of the transition temperatures [8C] as a function of

chain length (n)for the O-b-d-galactopyranosyl-tri-O-alkyl pentaerythri-

tols (I) 19a–f.

comparison. The dotted line in Figure 4 shows the odd/even

effects of the chain length. Note, alternating clearing points

reinforce the proof of purity of the samples.

Di-O-b-d-galactopyranosyl-di-O-alkyl

pentaerythritols

(II): The two aliphatic chain series of compounds, unlike

the three chain analogues, were found to exhibit only one

liquid crystal phase, the smectic A* phase. All of the materi-

als exhibited enantiotropic phases which possessed tempera-

ture ranges in the region of 1508C. The smectic A* phase

was characterised by the formation of focal-conic domains

where the elliptical and hyperbolic lines of optical disconti-

nuity are diagnostic for the presence of the A phase. At the

phase transition from the isotropic liquid decomposition oc-

curred with the release of gas. The resulting texture showed

large gas bubbles, with the mesophase sandwiched between

the bubbles (see Figure 4). Differential scanning calorimetry

also showed extensive decomposition at the clearing point

with large fluctuations occurring with respect to the base-

line.

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the effects of curvature of molecular packing on mesophase

formation.

Discussion

In the introduction it was described how previously the cur-

vature of packing can affect the self-organising and self-as-

sembling properties of thermotropic, as well as lyotropic,

liquid crystals.^[8c,d]In order to examine the effects of curva-

ture it is first instructive to examine the molecular structures

of the materials under investigation. The relative shapes of

the molecules were investigated via computer simulations

using an Apple Macintosh G5 computer and ChemDraw3D

as part of a ChemDraw Ultra 6.0 program. This programme

assumes that the molecules are in the gas phase at absolute

zero. For the purposes of comparison, Figure 5 shows the

minimised structures for the dodecyl homologues of series,

I, II and III.

Figure 4. Transition from isotropic liquid to smectic A* phase for di-O-b-

d-galactopyranosyl-di-O-hexadecyl pentaerythritol (C₁₆20h)(100. )

Focal-conic domains are clearly seen as elliptical and hyperbolic lines of

optical discontinuity.

In comparison to the three chain family of materials, I,

the two chain-two sugar system, II, because of the increased

degree of inter-molecular hydrogen bonding has much

higher clearing temperatures, that is, in the range of 1208C.

However, the higher clearing points and the incorporation

of an extra sugar unit leads to a increase susceptibility to-

wards decomposition. Nevertheless, the clearing point tran-

sition temperatures lie on a smooth curve, with the smectic

A* phase being introduced at the dihexyl homologue and

quickly saturating at the didodecyl member.

O-Alkyl-tri-O-b-d-galactopyranosyl pentaerythritols (III):

Only two of this series were prepared: the dodecyl (21 f)

and hexadecyl (21h)homologues. Both exhibit enantiotropic

cubic phases as predicted. However, the melting points are

higher in comparison to those found for series II. However,

these values probably reflect the higher degree of intramo-

lecular hydrogen bonding. Interestingly, the clearing point

temperatures are almost identical with respect to those ob-

tained for series II. This suggests at such high temperatures

the hydrogen bonding is possibly more dynamic and both

intra- as well as intermolecular hydrogen bonding are of im-

portance and as a consequence no increase is seen in the

clearing temperatures. Furthermore, these materials exhibit-

ed strong decomposition, which made it difficult to ascertain

their true clearing point values.

Figure 5. Minimised structures of the dodecyl homologues of series I, II

and III.

The two compounds were both found to exhibit an opti-

cally extinct phase formed upon cooling from the isotropic

liquid. The transition from the isotropic liquid to the cubic

phase was observed via the insertion of a phase plate into

the microscope above the objective and observing the

Becker line between the two phases. No birefringence was

observed even around air bubbles, and the phase was found

to be viscous when the sample was subjected to mechanic

shearing. These observations are consistent with the phase

being cubic. The detailed structure of the phase requires fur-

ther studies by X-ray diffraction; however, this is beyond

the scope of this study which is directed towards examining

As for all amphiphilic systems, the driving force for the

liquid crystal phase formation in these three cases is the

generation of a hydrogen-bonding network between adja-

cent galactose units, thereby, giving rise to the segregation

of the aliphatic chains from the carbohydrate head groups.

For series I, the compounds are composed of three chains

and one carbohydrate unit, and have wedge-like shapes with

the sugar units at the apices of the wedges. Consequently

these materials would be expected to exhibit cubic and col-

umnar mesophases that have inverted structures. Thus we

propose that the type of columnar phase exhibited by series

I is a hexagonal columnar phase with the individual mole-

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O-Alkyl Pentaerythritol–Galactose Derivatives

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cules disordered up and down the column axis as shown in

Figure 6. However, as noted above X-ray diffraction studies

would be necessary to clarify the detailed structure and to

determine the inter-columnar distances.

lyotropic systems, for example, the micellar units are found

to adopt a number of different conformations such as spher-

ical, oblate and prolate. However, from the diffraction stud-

ies of other amphiphilic systems displaying thermotropic dis-

continuous cubic phases there appears to be two potential

micellar structures, spherical and oblate, as shown in Fig-

ures 7 and 8.^[41–43]

Figure 6. Columnar structure of the hexagonal columnar phase formed by

series I.

Figure 8. Oblate micellar structure found in cubic phases.

In the columnar phase the materials probably adopt a rel-

atively flat conformation to enable them to self-organise

into a cylindrical columnar arrangement. However, at higher

temperatures where the molecules are in increased dynami-

cal motion, several of the compounds were also found to ex-

hibit cubic mesophases. As the three aliphatic chains are at-

tached to a tetrahedral shaped pentaerythritol core via very

flexible ether linkages, it can be assumed that alternative

molecular geometries are also possible. For example, the dy-

namical motion might induce the molecules to assume a

conical shape, rather than a wedge. For this conformational

volume, the best packing arrangement is spherical with the

cones pointing towards the centre as shown in Figure 7.

For materials of type III, the structures of the cubic meso-

phases are essentially the inverse of those of type I com-

pounds. The galactose units are this time located towards

the exterior of the micelle and the aliphatic chains are to-

wards the centre, as shown in Figure 9.

Figure 9. Packing of cone-shaped conformational volumes of the mole-

cules for the cubic phases of series III compounds.

For series II, with structures half way between series I

and III, not surprisingly the head groups are of a similar

cross-sectional size to those of the aliphatic chains. Thus

when the molecules pack together they will form a lamellar

smectic A* phase as predicted. Figure 10 shows the packing

structure of the molecules into a lamellar phase for the di-

dodecyl homologue. It can be seen from this Figure that the

degree of curvature in the packing is minimal.

From these studies and those made previously by our-

selves and others^[44–46]we can see that molecular shape and

the related curvature of packing has a similar impact on

thermotropic phases as it does for lyotropic systems. We can

place some of the molecular architectures into the phase di-

agram shown in Figure 1, and thereby relate the molecular

Figure 7. Packing of cone-shaped conformational volumes of the mole-

cules for series I compounds.

From the analysis of the liquid crystal properties of sys-

tems that have similar shapes to series I,^[41]it can be de-

duced that the isotropic mesophase observed is a discontinu-

ous cubic phase. The curvature introduced into the system

through the splay of the three chains for the compounds in

series I is thought to be sufficient to support the formation

of this type of mesophase. The structure of the discontinu-

ous cubic mesophase in this case consists of a cubic arrange-

ment of closed spherical or non-spherical micelle units. In

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P. Boullanger, J. W. Goodby et al.

these two materials it was not possible to create a full phase

diagram due to the effects of recrystallisation. However,

through the use of contact preparations it was possible to

observe a lamellar phase at the centre of the sample prepa-

ration which was characterised by hyperbolic and elliptical

lines of optical discontinuity. To either sides of the contact

preparation isotropic cubic phases were present, character-

ised by the presence of rectilinear lines with no elliptical or

hyperbolic optical discontinuities.

A full phase diagram between glycolipids possessing two

head groups and one chain and two chains and one head

group was reported by us previously,^[45]and, as predicted by

the relationship described above, a full range of mesophase

types was produced from one columnar phase to the other

columnar phase across the phase diagram as shown in

Figure 12.

Figure 10. Packing structure of the molecules into a lamellar phase for

the didodecyl homologue of series II.

shapes of rods, wedges and cones to mesophase formation

and stability (see Figure 11). Although the results apply to a

strongly microphase segregating amphiphilic system, they

should also apply to other microphase segregating systems

such as fluorocarbons/hydrocarbons. Thus this work unifies

lyotropic and thermotropic systems for all forms of amphi-

philes.

We can test this hypothesis via mixing of material designs

derived from certain parts of the phase diagram, for exam-

ple, if we mix compounds from series I with examples from

series III, then a lamellar phase should be obtained in the

50/50 region of the phase diagram. Indeed this is the case,

when a contact preparation is made between compounds

19 f and 21 f, both possessing dodecyl aliphatic chains, a la-

mellar phase appears in the centre of the defect texture

(characterised by ellipse and hyperbolic lines of optical dis-

continuities, result not shown). Unfortunately, because of

the large differences in transition temperatures between

Figure 12. Miscibility phase diagram [wt%] as a function of temperature

[8C] between compounds A and B.

Conclusion

In this study we have successfully demonstrated that the ef-

fects of molecular shape and curvature of packing in lyo-

tropic systems is transferable to thermotropic liquid crystals.

The results of this work are generally applicable to all forms

of amphiphiles that exhibit liquid crystallinity. However, it is

not clear whether or not this work will be applicable to

shape dependency without amphiphilicity which takes the

form of microphase segregation.

Figure 11. Effect of molecular shape and curvature of packing on meso-

phase formation in thermotropic liquid crystals.

5592

www.chemeurj.org

ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Chem. Eur. J. 2007, 13, 5585 – 5600

O-Alkyl Pentaerythritol–Galactose Derivatives

FULL PAPER

(300 MHz, CDCl₃): d=1.27 ppm (m, 36H, 18CH₂alkyl chains)and

¹³C NMR (75 MHz, CDCl₃): d=31.89, 29.74, 29.58, 29.46, 29.37, 29.29,

26.17, 22.48 ppm (CH₂alkyl chains); IR (KBr disc): n˜ = 3543 (OH),

1108 (CO), 2934, 2861, 1465, 1375, 1051, 723 cm^ꢀ1(C-H, C-C); MS (ES):

m/z: calcd for: 514; found: 516 [M+2]⁺, 352, 299, 247, 226, 210, 197, 173,

155, 141, 127, 115, 100, 95, 71.

Experimental Section

Materials and methods: Pyridine was dried by boiling with CaH₂prior to

distillation. Dichloromethane was washed twice with water, dried with

CaCl₂and distilled over P₂O₅. Methanol was distilled from magnesium.

Tetrahydrofuran was distilled over sodium/benzophenone. Pyridine, THF

and CH₂Cl₂were stored over 4 molecular sieves and MeOH over 3

molecular sieves. Melting points were determined on a Büchi apparatus

and were uncorrected. Thin layer chromatography was performed on alu-

minium sheets coated with Silica gel 60 F₂₅₄(E. Merck). Compounds

were visualized by spraying the TLC plates with dilute 15% aq H₂SO₄,

followed by charring at 1508C for a few min. Column chromatography

was performed on silica gel Geduran Si 60 (Merck). Optical rotations

were recorded on a Perkin Elmer 241 polarimeter in a 1 dm³cell at

218C. ¹H and ¹³C NMR spectra were recorded with a Bruker AC-200

spectrometer (working at 200 and 50 MHz)or a JEOL JNM-LA400 spec-

trometer (working at 400 and 100 MHz), respectively, with Me₄Si as in-

ternal standard. Elemental analyses were performed by the “Laboratoire

Central dꢁAnalyses du CNRS” (Vernaison, France). Mass spectra were

recorded on a Finnigan-MAT 1020 automated GC/MS spectrometer or a

Shimatzu GC/MS-QP5050 A Gas Chromatograph spectrometer with

electron impact. Phase identifications and determination of phase transi-

tion temperatures were carried out, concomitantly, by thermal polarized

light microscopy using either a Zeiss Universal polarizing transmitted

light microscope equipped with a Mettler FP52 microfurnace in conjunc-

tion with an FP50 Central Processor. Photomicrographs were obtained

using a Zeiss polarizing light microscope equipped with a Nikon AFM

camera. Differential scanning calorimetry was also used to confirm the

phase transition temperatures determined by optical microscopy. Differ-

ential scanning thermograms (scan rate 108Cmin^ꢀ1)were obtained using

a Perkin Elmer DSC 7 PC system operating on DOS software.

Tri-O-decyl pentaerythritol (2d): Obtained as described above, after pu-

rification by column chromatography (EtOAc/hexane 1:9)as a yellow oil

(3.2 g, 33%); homogeneous by TLC, R_f=0.36; ¹H and ¹³C NMR spectra

showed no peaks additional to those interpreted for the target com-

pound; they were similar to those recorded for 2a, except for ¹H NMR

(300 MHz, CDCl₃): d=1.26 ppm (m, 42H, 21CH₂alkyl chains)and

¹³C NMR (75 MHz, CDCl₃): d=31.87, 29.60, 29.55, 29.54, 29.43, 29.30,

26.13, 22.64 ppm (CH₂alkyl chains); IR (KBr disc): n˜ = 3543 (OH),

1109 (CO), 2932, 2861, 1466, 1376 cm^ꢀ1(C-H, C-C); MS (ES): m/z: calcd

for: 556; found: 558 [M+2]⁺, 539, 513, 490, 453, 430, 400, 380, 353, 327,

288, 261, 240, 223, 210, 196, 187, 155, 140, 108, 98, 91, 84, 70.

Tri-O-undecyl pentaerythritol (2e): Obtained as described above, after

purification by column chromatography (EtOAc/hexane 1:9)as a yellow

1

oil (3.4 g, 26%); homogeneous by TLC, R_f=0.38; H and ¹³C NMR spec-

tra showed no peaks additional to those interpreted for the target com-

pound; they were similar to those recorded for 2a, except for ¹H NMR

(300 MHz, CDCl₃): d=1.26 ppm (m, 48H, 24CH₂alkyl chains)and

¹³C NMR (75 MHz, CDCl₃): d=31.88, 29.60, 29.54, 29.44, 29.32, 26.13,

22.64 ppm (CH₂alkyl chains); IR (KBr disc): n˜

= 3543 (OH), 1109

(CO), 2931, 2861, 1466, 1376, 723 cm^ꢀ1(C-H, C-C); MS (ES): m/z: calcd

for: 598; found: 600 [M+2]⁺, 570, 539, 510, 469, 445, 408, 380, 355, 327,

271, 253, 242, 224, 201, 167, 154, 141, 112, 98, 85, 69.

Tri-O-dodecyl pentaerythritol (2 f): Obtained as described above, after

purification by column chromatography (EtOAc/petroleum ether 1:20)as

an oily material (3.2 g, 23%); homogeneous by TLC, R_f=0.44; ¹H and

¹³C NMR spectra showed no peaks additional to those interpreted for the

target compound; they were similar to those recorded for 2a, except for

¹H NMR (200 MHz, CDCl₃): d=1.27 ppm (m, 54H, 27CH₂alkyl chains)

and ¹³C NMR (50 MHz, CDCl₃): d=1.96, 29.73, 29.69, 29.62, 29.50, 29.40,

26.21, 22.70 ppm (CH₂alkyl chains); MS (ES): m/z: calcd for: 641;

found: 642 [M+H]⁺; elemental analysis calcd (%)for C ₄₁H₈₄O₄(641.08):

C 76.81, H 13.21; found: C 76.87, H 13.37.

General procedure for the preparation of tri-O-alkyl pentaerythritol de-

rivatives 2a–h: Pentaerythritol (1)(3.0 g, 22.0 mmol)was added to a

freshly prepared aq. NaOH solution (35.2 g NaOH and 30 mL water)and

the resulting mixture was heated at 808C with stirring, for 1 h. Alkyl bro-

mide (66.0 mmol)and tetrabutylammonium bromide (0.88 g, 2.75 mmol)

were then added and heating was maintained for a further 5 h. After

cooling, the mixture was partitioned between CH₂Cl₂(100 mL)and water

(100 mL)and the organic phase was washed with water (350 mL,)

dried (Na₂SO₄)and concentrated. The crude product was purified by

column chromatography affording the pure tri-O-alkyl products.

Tri-O-tetradecyl pentaerythritol (2g): Obtained as described above, after

purification by column chromatography (EtOAc/petroleum ether 1:20)as

a white solid (2.3 g, 15%); homogeneous by TLC, R_f=0.44; m.p. 35–

368C; ¹H and ¹³C NMR spectra showed no peaks additional to those in-

terpreted for the target compound; they were similar to those recorded

for 2 f, except for ¹H NMR (200 MHz, CDCl₃): d=1.27 ppm (m, 66H,

33CH₂alkyl chains); elemental analysis calcd (%) for C ₄₇H₉₆O₄(725.24):

C 77.83, H 13.34; found: C 77.57, H 13.27.

Tri-O-hexyl pentaerythritol (2a): Obtained as described above after pu-

rification by column chromatography (EtOAc/petroleum ether 1:15)as

an oily material (1.45 g, 17%); homogeneous by TLC, R_f=0.40;

¹H NMR (200 MHz, CDCl₃): d=3.71 (d, 2H, J=6.0 Hz, CH₂OH), 3.44

(s, 6H, 3CH₂OAlk)₃), 3.39 (t, 6H, J=6.2 Hz, 3OCH₂Alk), 3.16 (t, 1H,

CH₂OH), 1.54 (m, 6H, 3OCH₂CH₂Alk), 1.30 (m, 18H, 9CH₂alkyl

chains), 0.89 ppm (t, 9H, 3CH₃alkyl chains); ¹³C NMR (50 MHz,

CDCl₃): d=71.67, 71.39 (CH₂OCH₂Alk), 66.37 (CH₂OH), 44.76

Tri-O-hexadecyl pentaerythritol (2h): Obtained as described above, after

purification by column chromatography (EtOAc/petroleum ether 1:20)as

a white solid (1.9 g, 11%); homogeneous by TLC, R_f=0.45; m.p. 44–

458C; ¹H and ¹³C NMR spectra showed no peaks additional to those in-

terpreted for the target compound; they were similar to those recorded

for 2 f, except for ¹H NMR (200 MHz, CDCl₃): d=1.27 ppm (m, 78H,

39CH₂alkyl chains); elemental analysis calcd (%) for C ₅₃H₁₀₈O₄(809.39):

C 78.64, H 13.45; found: C 78.62, H 13.55.

(C(CH₂)₄), 31.64, 29.53, 25.82, 22.60 (CH₂alkyl chains), 14.13 ppm

(CH₃); elemental analysis calcd (%) for C ₂₃H₄₈O₄(388.61): C 71.08, H

12.45; found: C 70.68, H 12.64.

A

Tri-O-heptyl pentaerythritol (2b): Obtained as described above, after pu-

rification by column chromatography (EtOAc/hexane 1:9)as a yellow oil

(2.8 g, 30%); homogeneous by TLC, R_f=0.35; ¹H and ¹³C NMR spectra

showed no peaks additional to those interpreted for the target com-

pound; they were similar to those recorded for 2a, except for ¹H NMR

(300 MHz, CDCl₃): d=1.29 ppm (m, 24H, 12CH₂alkyl chains)and

¹³C NMR (75 MHz, CDCl₃): d=31.87, 29.61, 29.16, 26.16, 22.66 ppm

(CH₂alkyl chains); IR (KBr disc): n˜ = 3539 (OH), 1108 (CO), 2935,

2863, 1466, 1376, 1051 cm^ꢀ1(C-H, C-C); MS (ES): m/z: calcd for: 430;

found: 431 [M+H]⁺, 382, 333, 295, 269, 243, 219, 198, 181, 169, 156, 145,

112, 98, 71.

General procedure for the preparation of O-benzylidene-di-O-alkyl pen-

taerythritol derivatives 4a,f–h: O-Benzylidene pentaerythritol (3)^[35]

(1.35 g, 6.02 mmol)was added to a freshly prepared 50% aq. NaOH solu-

tion (7 mL)and the mixture was heated at 80 8C for 30 min under stir-

ring. Alkyl bromide (24.0 mmol)and tetrabutylammonium bromide

(0.77 g, 2.4 mmol)were successively added and heating was maintained

for 8 h. After cooling to RT, water was added (100 mL)and the mixture

was extracted with CHCl₃(340 mL); the combined organic phases were

washed with water (225 mL), dried (Na₂SO₄)and concentrated. The

crude product was purified by column chromatography.

Tri-O-nonyl pentaerythritol (2c): Obtained as described above, after pu-

rification by column chromatography (EtOAc/hexane 1:9)as a yellow oil

(1.5 g, 20%); homogeneous by TLC, R_f=0.35; ¹H and ¹³C NMR spectra

showed no peaks additional to those interpreted for the target com-

pound; they were similar to those recorded for 2a, except for ¹H NMR

O-Benzylidene-di-O-hexyl pentaerythritol (4a): Prepared as described

above using hexyl bromide (3.4 mL, 24.0 mmol). The crude product was

purified by column chromatography (EtOAc/petroleum ether 1:15)af-

fording the pure product 4a as an oily material (1.95 g, 83%). R_f=0.50;

Chem. Eur. J. 2007, 13, 5585 – 5600

ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemeurj.org

5593

P. Boullanger, J. W. Goodby et al.

¹H NMR (200 MHz, CDCl₃): d=7.52–7.27 (m, 5H, C₆H₅), 5.44 (s, 1H,

CHC₆H₅), 4.11 (d, 2H, J_a,e=11.2 Hz, 2H-eq), 3.90 (d, 2H, 2H-ax), 3.73

(s, 2H, CH₂OAlk), 3.48 (t, 2H, J=6.5 Hz, OCH₂Alk), 3.38 (t, 2H, J=

6.5 Hz, OCH₂Alk), 3.25 (s, 2H, CH₂OAlk), 1.59 (m, 4H,

2OCH₂CH₂Alk), 1.31 (m, 12H, 6CH₂alkyl chains), 0.91 ppm (t, 6H,

2CH₃alkyl chains); ¹³C NMR (50 MHz, CDCl₃): d=138.63, 128.90,

128.31, 126.20 (C₆H₅), 101.79 (CHC₆H₅), 71.82, 71.69, 70.85, 70.30, 69.40

Di-O-hexadecyl pentaerythritol (5h): Prepared in 88% yield as described

above from 4h. Purification of the crude product by column chromatog-

raphy (EtOAc/petroleum ether 1:2)afforded the pure compound 5h as a

white solid. R_f=0.74; m.p. 69–708C (lit.:^[32]m.p. 70–718C); ¹H and

¹³C NMR spectra were similar to those recorded for 5 f, except for

¹H NMR (200 MHz, CDCl₃): d=1.26 ppm (m, 52H, 26CH₂alkyl chains).

General procedure for the preparation of O-benzylidene-O-alkyl pen-

taerythritol derivatives 6 f,h: A suspension of O-benzylidene pentaery-

thritol 3^[35](2.24 g, 10.00 mmol)and dibutyltin oxide (2.96 g, 11.89 mmol)

was heated under reflux in dry MeOH (30 mL)at 80 8C for 6 h. The sol-

vent was removed by evaporation and the residue was carefully dried

under high vacuum. The product was dissolved in DMF (60 mL), alkyl

bromide (16 mmol)and caesium fluoride (4.03 g, 26.5 mmol)were added

and the mixture was stirred for 24 h at RT. Ethyl acetate (50 mL)and

water (1.5 mL)were then added and the mixture was stirred for 1 h.

After filtration and concentration, the residue was dissolved in CH₂Cl₂

(100 mL)and the organic phase was washed with water (250 mL,)

dried (Na₂SO₄)and concentrated. The crude product was purified by

column chromatography to afford mixtures of cis and trans isomers.

(CH₂OAlk, OCH₂Alk, CH₂OCHC₆H₅), 38.97 (C(CH₂)₄), 31.80, 31.75,

A

29.70, 29.56, 25.92, 22.72 (CH₂alkyl chains), 14.13 ppm (CH₃alkyl

chains); elemental analysis calcd (%) for C ₂₄H₄₀O₄(392.56): C 73.42, H

10.27; found: C 73.29, H 9.87.

O-Benzylidene-di-O-dodecyl pentaerythritol (4 f): Prepared as described

above for 4a, using dodecyl bromide (5.7 mL, 24.0 mmol). The pure

product 4 f was recovered after purification by column chromatography

(EtOAc/petroleum ether 1:20)as a white solid (2.45 g, 75%.) R_f=0.39;

m.p. 40–418C; ¹H and ¹³C NMR spectra were similar to those recorded

for 4a, except for ¹H NMR (200 MHz, CDCl₃): d=1.28 ppm (m, 36H,

18CH₂alkyl chains); elemental analysis calcd (%) for C ₃₆H₆₄O₄(560.87):

C 77.08, H 11.50; found: C 76.65, H 11.27.

O-Benzylidene-di-O-tetradecyl pentaerythritol (4g): Prepared as de-

scribed above for 4a, using tetradecyl bromide (7.15 mL, 24.0 mmol).

The pure product 4g was recovered after purification by column chroma-

tography (EtOAc/petroleum ether 1:15)as a white solid (3.12 g, 84%.)

R_f=0.44; m.p. 458C; ¹H and ¹³C NMR spectra were similar to those re-

corded for 4a, except for ¹H NMR (200 MHz, CDCl₃): d=1.27 ppm (m,

44H, 22CH₂alkyl chains); elemental analysis calcd (%) for C ₄₀H₇₂O₄

(616.98): C 77.86, H 11.76; found: C 77.66, H 12.15.

O-Benzylidene-O-dodecyl pentaerythritol (6 f): Prepared as described

above in 63% yield after purification by column chromatography

EtOAc/petroleum ether 2:5). The less polar isomer (R_f=0.69)could be

obtained as a solid. M.p. 468C; ¹H NMR (200 MHz, CDCl₃): d=7.52–

7.35 (m, 5H, C₆H₅), 5.44 (s, 1H, CHC₆H₅), 4.18 (2d, 2H, J_a,e=11.9 Hz,

2H-eq), 4.05 (d, 2H, J=6.0 Hz, CH₂OH), 3.78 (2d, 2H, J=11.9 Hz, 2H-

ax), 3.40 (t, 2H, OCH₂Alk), 3.29 (s, 2H, CH₂OAlk), 2.46 (t, 1H,

CH₂OH), 1.57 (m, 2H, OCH₂CH₂Alk), 1.27 (m, 18H, 9CH₂alkyl chain),

0.89 ppm (t, 3H, CH₃alkyl chain); ¹³C NMR (50 MHz, CDCl₃): d=

138.33, 128.98, 128.30, 126.21 (C₆H₅), 101.96 (CHC₆H₅), 72.89, 72.16,

O-Benzylidene-di-O-hexadecyl pentaerythritol (4h): Prepared as de-

scribed above for 4a, using hexadecyl bromide (7.3 mL, 24.0 mmol). The

pure product 4h was recovered after purification by column chromatog-

raphy (EtOAc/petroleum ether 1:15)as a white solid (3.25 g, 80%); R_f=

0.46; m.p. 58–598C (lit.:^[32]m.p. 59–608C); ¹H and ¹³C NMR spectra were

similar to those recorded for 4a, except for ¹H NMR (200 MHz, CDCl₃):

d=1.27 ppm (m, 52H, 26CH₂alkyl chains).

69.97, 69.97 (C

N

29.72, 29.70, 29.50, 29.44, 26.16, 22.76 (CH₂alkyl chain), 14.20 ppm (CH₃

alkyl chain).; elemental analysis calcd (%) for C₂₄H₄₀O₄(392.56): C

73.42, H 10.27; found: C 73.43, H 10.33.

The more polar isomer (R_f=0.59)was obtained as an oil, contaminated

by dodecyl alcohol. ¹H NMR (200 MHz, CDCl₃): d=7.52–7.35 (m, 5H,

C₆H₅), 5.45 (s, 1H, CHC₆H₅), 4.19 (2d, 2H, J=11.9 Hz, 2H-eq), 3.94 (s,

2H, CH₂OAlk), 3.76 (2d, 2H, J=11.9 Hz, 2H-ax), 3.57–3.50 (m, 4H,

CH₂OH, OCH₂Alk), 2.89 (t, 1H, CH₂OH), 1.57 (m, 2H, OCH₂CH₂Alk),

1.27 (m, 18H, 9CH₂alkyl chain), 0.89 ppm (t, 3H, CH₃alkyl chain);

¹³C NMR (50 MHz, CDCl₃): d=138.25, 129.05, 128.36, 126.12 (C₆H₅),

General procedure for the preparation of di-O-alkyl pentaerythritols

5a,f–h: Compounds 4a,f–h (5.0 mmol)were dissolved in a mixture of dry

EtOH (8 mL)and freshly distilled cyclohexene (4 mL.) Pd(OH) ₂/C

(200 mg)was then added and the suspension was heated under reflux for

6 h under argon. After cooling, filtration through Celite and concentra-

tion, the residue was purified on a short column of silica gel.

102.12 (CHC₆H₅), 73.24, 72.22, 70.60, 70.60 (C

38.40 (C(OCH₂)₄), 31.97, 29.71, 29.70, 29.50, 29.41, 26.20, 22.74 (CH₂

alkyl chain), 14.17 ppm (CH₃alkyl chain).

A

Di-O-hexyl pentaerythritol (5a): Prepared in 88% yield as described

above from 4a. Purification of the crude product by column chromatog-

raphy (EtOAc/petroleum 1:1 ether)afforded the pure compound 5a as

an oily material. R_f=0.67; ¹H NMR (200 MHz, CDCl₃): d=3.64 (d, 4H,

2CH₂OH), 3.50 (s, 4H, 2CH₂OAlk), 3.42 (m, 4H, 2OCH₂Alk), 2.93 (s,

2H, 2OH), 1.55 (m, 4H, 2OCH₂CH₂Alk), 1.29 (m, 12H, 6CH₂alkyl

chains), 0.90 ppm (t, 6H, 2CH₃alkyl chains); ¹³C NMR (50 MHz,

AHCTREUNG

O-Benzylidene-O-hexadecyl pentaerythritol (6h): Prepared as described

above in 68% yield after purification by column chromatography

(EtOAc/petroleum ether 2:5). A pure fraction of the less polar isomer

(R_f=0.63 in EtOAc/petroleum ether 1:3)could be obtained as a solid.

M.p. 528C; ¹H and ¹³C NMR spectra were similar to those recorded for

6 f, except for ¹H NMR (200 MHz, CDCl₃): d=1.27 ppm (m, 26H,

13CH₂alkyl chain); elemental analysis calcd (%) for C ₃₀H₄₈O₄(448.66):

C 74.95, H 10.78; found: C 74.65, H 10.98.

CDCl₃): d=72.13, 71.83 (CH₂OAlk, OCH₂Alk), 44.75 (C(CH₂)₄), 31.57,

N

29.43, 25.73, 22.52 (CH₂alkyl chains), 14.02 ppm (CH₃alkyl chains); ele-

mental analysis calcd (%)for C ₁₇H₃₆O₄0.25H₂O (308.96): C 66.09, H

11.91; found: C 66.10, H 11.82.

The more polar isomer (R_f=0.63 in EtOAc/petroleum ether 1:3)was ob-

tained as an oil, contaminated by hexadecyl alcohol; ¹H and ¹³C NMR

spectra were similar to those recorded for 6 f, except for ¹H NMR

(200 MHz, CDCl₃): d=1.27 ppm (m, 26H, 13CH₂alkyl chain).

Di-O-dodecyl pentaerythritol (5 f): Prepared in 95% yield as described

above from 4 f. Purification of the crude product by column chromatogra-

phy (EtOAc/petroleum ether 1:1)afforded the pure compound 5 f as a

1

white solid. R_f=0.70; m.p. 57–588C; H and ¹³C NMR spectra were simi-

lar to those recorded for 5a, except for ¹H NMR (200 MHz, CDCl₃): d=

1.27 ppm (m, 36H, 18CH₂alkyl chains)and ¹³C NMR (50 MHz, CDCl₃):

d=31.96, 29.71, 29.67, 29.56, 29.48, 29.40, 26.18, 22.73 ppm (CH₂alkyl

chains); elemental analysis calcd (%) for C ₂₉H₆₀O₄(472.77): C 73.67, H

12.79; found: C 73.29, H 12.44.

General procedure for the preparation of O-alkyl-O-benzyl pentaerythri-

tol derivatives 7 f,h: A mixture of O-benzylidene-O-alkyl pentaerythritols

6 f,h (6.00 mmol), borane trimethylamine complex (1.824 g, 25.00 mmol)

and crushed activated 4 molecular sieves (4 g)in dry THF (40 mml)

was cooled to 08C. Aluminium trichloride (3.35 g, 25.05 mmol)was then

added over 30 min; the mixture was allowed to reach RT and stirring was

maintained for 16 h. After filtration, the solution was concentrated and

the residue was dissolved in ethyl acetate (100 mL)and washed with sa-

turated aq. NaHCO₃(350 mL). The organic phase was concentrated

and the residue was treated overnight with stirring in 1m aq. HCl

(50 mL). The product was extracted with CH₂Cl₂(100 mL)and the or-

ganic phase was dried. After concentration, the crude residue was puri-

fied by column chromatography.

Di-O-tetradecyl pentaerythritol (5g): Prepared in 85% yield as described

above from 4g. Purification of the crude product by column chromatog-

raphy (EtOAc/petroleum ether 1:1)afforded the pure compound 5g as a

white solid. R_f=0.57 (EtOAc/petroleum ether 1:2); m.p. 62 8C; ¹H and

¹³C NMR spectra were similar to those recorded for 5 f, except for

¹H NMR (200 MHz, CDCl₃): d=1.27 ppm (m, 44H, 22CH₂alkyl chains):

elemental analysis calcd (%)for C ₃₃H₆₈O₄(528.87): C 74.94, H 12.96;

found: C 74.67, H 13.04.

5594

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ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Chem. Eur. J. 2007, 13, 5585 – 5600

O-Alkyl Pentaerythritol–Galactose Derivatives

FULL PAPER

O-Benzyl-O-dodecyl pentaerythritol (7 f): Obtained in 65% yield, as de-

scribed above from 6 f, after purification by column chromatography

(EtOAc/petroleum ether 1:1)as an oily material. R_f=0.40; ¹H NMR

(200 MHz, CDCl₃): d=7.39–7.29 (m, 5H, C₆H₅), 4.52 (s, 2H, CH₂C₆H₅),

3.68 (s, 4H, 2CH₂OH), 3.56, 3.52 (2s, 4H, CH₂OAlk, CH₂OBn), 3.41 (t,

2H, J=6.5 Hz, OCH₂Alk), 2.75 (m, 2H, 2CH₂OH), 1.55 (m, 2H,

OCH₂CH₂Alk), 1.27 (m, 18H, 9CH₂alkyl chain), 0.89 ppm (t, 3H, CH₃

alkyl chain); ¹³C NMR (50 MHz, CDCl₃): d=138.18, 128.43, 127.69,

126.51 (C₆H₅), 73.68 (CH₂C₆H₅), 72.54, 72.00, 71.52 (CH₂OCH₂Alk,

chains); elemental analysis calcd (%) for C ₈₁H₁₂₂O₁₃(1303.79): C 74.61,

H 9.43; found: C 74.67, H, 9.57.

O-(2,3,4,6-Tetra-O-benzoyl-b-d-galactopyranosyl)-tri-O-hexadecyl pen-

taerythritol (11h): Prepared as described above in 76% yield from tri-O-

hexadecyl pentaerythritol 2h. The crude product was purified by column

chromatography (EtOAc/petroleum ether 1:9)to yield an oily material.

1

R_f=0.50; [a]_D=+37.88 (c = 1.0, CHCl₃); H and ¹³C NMR spectra were

1

similar to those recorded for 11 f, except for H NMR (200 MHz, CDCl₃):

d=1.26 ppm (m, 78H, 39CH₂alkyl chains); elemental analysis calcd (%)

CH₂OBn), 64.66 (CH₂OH), 44.98 (C(OCH₂)₄), 31.98, 29.73, 29.70, 29.67,

A

for C₈₇H₁₃₄O₁₃(1387.94): C 75.28, H 9.73; found: C 75.25, H, 9.73.

29.59, 29.42, 26.19, 22.74 (CH₂alkyl chain), 14.17 ppm (CH₃alkyl chain);

elemental analysis calcd (%)for C ₂₄H₄₂O₄(394.58): C 73.05, H 10.73;

found: C 73.19, H 10.66.

General procedure for the preparation of O-(2,3,4,6-tri-O-acetyl-b-d-gal-

actopyranosyl)-tri-O-alkyl pentaerythritol derivatives (12a–h)

Method A: A mixture of 2,3,4,6-tetra-O-acetyl-a-d-galactopyranosyl bro-

mide (9)^[38](0.411 g, 1.00 mmol), alcohol, 2a,f–h (0.5 mmol)and crushed

activated 4 molecular sieves (0.4 g)in freshly distilled acetonitrile

(4 mL)was stirred for 10 min under argon. 2,3-Dichloro-5,6-dicyano-1,4-

benzoquinone (DDQ, 0.110 g, 0.50 mmol)and iodine (0.252 g, 1.0 mmol)

were then added and the solution was stirred for 6 h at RT. After filtra-

tion and concentration, the residue was dissolved in CH₂Cl₂(100 mL)

and the organic phase was washed with saturated aq Na₂S₂O₃(225 mL),

dried (Na₂SO₄)and concentrated. The product was purified by column

chromatography.

O-Benzyl-O-hexadecyl pentaerythritol (7h): Obtained as described

above from 6h, in 54% yield after purification by column chromatogra-

phy (EtOAc/petroleum ether 2:3)as a white solid. R_f=0.48; m.p. 478C;

¹H and ¹³C NMR spectra were similar to those recorded for 7 f, except

for ¹H NMR (200 MHz, CDCl₃): d=1.27 ppm (m, 26H, 13CH₂alkyl

chain); elemental analysis calcd (%) for C ₂₈H₅₀O₄(450.68): C 74.62, H

11.18; found: C 74.41, H 11.16.

General procedure for the preparation of tri-O-alkyl-O-(2,3,4,6-tetra-O-

benzoyl-b-d-galactopyranosyl) pentaerythritol derivatives (11a,f–h):

Compounds 2a,f–h (0.75 mmol)and 2,3,4,6-tetra- O-benzoyl-a-d-galacto-

pyranosyl trichloroacetimidate (8)^[14,36](0.584 g, 0.79 mmol)were dis-

solved in dry CH₂Cl₂(4.5 mL)in the presence of crushed activated 4

molecular sieves (0.4 g)and the suspension was cooled to 0 8C with stir-

Method B: Compounds 2a,f–h (0.75 mmol)and 2,3,4,6-tetra- O-acetyl-a-

d-galactopyranosyl trichloroacetimidate (10)^[39](0.406 g, 0.83 mmol)were

dissolved in dry CH₂Cl₂(4 mL)in the presence of crushed activated 4

molecular sieves (0.4 g)and the suspension was cooled to ꢀ208C with

stirring. A solution of TMSOTf (15 mL, 0.083 mmol)in CH ₂Cl₂(0.5 mL)

was added over 1 h and the mixture was stirred overnight at ꢀ208C. The

mixture was neutralized by addition of triethylamine (20 mL, 0.14 mmol),

then allowed to reach RT; after filtration through Celite, and concentra-

tion, the crude product was purified by column chromatography.

ring. A solution of TMSOTf (15 mL, 0.083 mmol)in CH Cl₂(0.5 mL)was

2

added over 1 h and the mixture was stirred overnight at 08C. After filtra-

tion through Celite, and addition of CH₂Cl₂(50 mL), the organic phase

was washed with saturated aq NaHCO₃, dried and concentrated to afford

the crude product which was purified by column chromatography.

Method C: A mixture of the respective alcohol, 2b–e (2.3 mmol), mercu-

ry cyanide (0.88 g, 3.5 mmol)mercury bromide (1.26 g, 3.50 mmol)and

anhydrous CH₂Cl₂(100 mL)was stirred under nitrogen. To this was

added galactosyl bromide 9^[38](2.47 g, 6.90 mmol)in anhydrous CH ₂Cl₂

(50 mL)dropwise over 30 min, after which the mixture was stirred over-

night. The resulting suspension was diluted with CH₂Cl₂(200 mL)was

washed with 1m potassium bromide (5100 mL)and water (5100 mL).

The organic layer was dried (MgSO₄)and the solvent removed in vacuo

to yield a pale yellow oil which was purified by column chromatography

(CH₂Cl₂/diethyl ether 4:1)to yield a clear oil which was homogeneous on

TLC.

O-(2,3,4,6-Tetra-O-benzoyl-b-d-galactopyranosyl)-tri-O-hexyl pentaery-

thritol (11a): Prepared as described above in 74% yield from tri-O-hexyl

pentaerythritol 2a. The crude product was purified by column chroma-

tography (EtOAc/petroleum ether 1:6)to yield an oily material. R_f=

0.53; [a]_D=+52.98 (c = 1.0, CHCl₃); ¹H NMR (200 MHz, CDCl₃): d=

8.12–7.21 (m, 20H, 4C₆H₅CO), 6.01 (dd, 1H, J_3,4=3.4, J_4,5=0.5 Hz, H-4),

5.80 (dd, 1H, J_1,2=7.8, J_2,3=10.4 Hz, H-2), 5.63 (dd, 1H, H-3), 4.79 (d,

1H, H-1), 4.70 (dd, 1H, J_5,6a=6.0, J_6a,6b=10.9 Hz, H-6a), 4.41 (dd, 1H,

J

_5,6b=7.2 Hz, H-6b), 4.29 (ddd, 1H, H-5), 4.01, 3.59 (2d, 2H, J=9.4 Hz,

CH₂OC-1), 3.33–3.18 (m, 12H, 3CH₂OCH₂Alk), 1.44 (m, 6H,

3OCH₂CH₂Alk), 1.27 (m, 18H, 9CH₂alkyl chains), 0.89 ppm (t, 9H,

3CH₃alkyl chains); ¹³C NMR (50 MHz, CDCl₃): d=166.00, 165.66,

165.60, 165.18 (COC₆H₅), 133.55, 133.24, 130.08–128.31 (C₆H₅), 102.45

(C-1), 71.76 (OCH₂Alk), 71.21 (C-3), 71.21 (C-5), 70.18 (C-2), 69.76

(CH₂OC-1), 69.33 (CH₂OAlk), 68.28 (C-4), 61.96 (C-6), 45.43 (C-

O-(2,3,4,6-Tetra-O-acetyl-b-d-galactopyranosyl)-tri-O-hexyl pentaerythri-

tol (12a): Prepared from the alcohol 2a in 76% yield (Method A)or

40% yield (Method B)after purification by column chromatography

(EtOAc/petroleum ether 1:3)as an oily material. R_f=0.54; [a]_D=ꢀ11.08

(c = 1.0, CHCl₃); ¹H NMR (200 MHz, CDCl₃): d=5.38 (dd, 1H, J_3,4

=

A

3.4, J_4,5=0.5 Hz, H-4), 5.20 (dd, 1H, J_1,2=7.8, J_2,3=10.5 Hz, H-2), 4.99

(dd, 1H, H-3), 4.42 (d, 1H, H-1), 4.18 (dd, 1H, J_5,6a=6.9, J_6a,6b=11.1 Hz,

H-6a), 4.12 (dd, 1H, J_5,6b=7.0 Hz, H-6b), 3.90, 3.49 (2 d, 2H, J=9.7 Hz,

CH₂OC-1), 3.86 (ddd, 1H, H-5), 3.38–3.28 (m, 12H, 3CH₂OCH₂Alk),

2.15, 2.06, 2.05, 1.99 (4s, 12H, 4CH₃COO), 1.52 (m, 6H,

3OCH₂CH₂Alk), 1.29 (m, 18H, 9CH₂alkyl chains), 0.89 ppm (t, 9H,

3CH₃alkyl chains); ¹³C NMR (50 MHz, CDCl₃): d=170.17, 170.17,

170.00, 169.04 (COCH₃), 101.98 (C-1), 71.40 (OCH₂Alk), 70.93 (C-3),

70.39 (C-5), 69.54 (CH₂OC-1), 69.33 (CH₂OAlk), 69.07 (C-2), 67.02 (C-

alkyl chains); elemental analysis calcd (%) for C ₅₇H₇₄O₁₃(967.16): C

70.78, H 7.71; found: C 70.85, H 8.01.

O-(2,3,4,6-Tetra-O-benzoyl-b-d-galactopyranosyl)-tri-O-dodecyl pentaer-

ythritol (11 f): Prepared as described above in 73% yield from tri-O-do-

decyl pentaerythritol 2 f. The crude product was purified by column chro-

matography (EtOAc/petroleum ether 1:5)to yield an oily material. R_f=

0.73; [a]_D=+43.78 (c = 1.0, CHCl₃); ¹H and ¹³C NMR spectra were simi-

1

lar to those recorded for 11a, except for H NMR (200 MHz, CDCl₃): d

=

1.27 ppm (m, 54H, 27CH₂alkyl chains)and ¹³C NMR (50 MHz,

4), 61.07 (C-6), 45.28 (C(CH₂O)₄), 31.62, 29.56, 25.85, 22.60 (CH₂alkyl

A

CDCl₃): d=32.01, 29.78–29.46, 26.30, 22.76 ppm (CH₂alkyl chains); ele-

mental analysis calcd (%)for C ₇₅H₁₁₀O₁₃(1219.63): C 73.86, H 9.09;

found: C 73.97, H 9.35.

chains), 13.98 ppm (CH₃alkyl chains); elemental analysis calcd (%) for

C₃₇H₆₆O₁₃(718.90): C 61.81, H 9.25; found: C 61.61, H 9.27.

O-(2,3,4,6-Tetra-O-acetyl-b-d-galactopyranosyl)-tri-O-heptyl

pentaery-

O-(2,3,4,6-Tetra-O-benzoyl-b-d-galactopyranosyl)-tri-O-tetradecyl pen-

taerythritol (11g): Prepared as described above in 72% yield from tri-O-

tetradecyl pentaerythritol 2g. The crude product was purified by column

chromatography (EtOAc/petroleum ether 1:9)to yield an oily material.

thritol (12b): Prepared from the alcohol 2b in 66% yield (Method C)

after purification by column chromatography. Oil; homogeneous by TLC,

R_f=0.54; [a]_D=ꢀ9.08 (c = 1.0, CHCl₃); ¹H and ¹³C NMR spectra were

similar to those recorded for 12a, except for ¹H NMR (400 MHz,

1

R_f=0.50; [a]_D=+40.38 (c = 1.0, CHCl₃); H and ¹³C NMR spectra were

CDCl₃): d

=

1.27 ppm (m, 24H, 12 CH₂alkyl chains)and ¹³C NMR

1

similar to those recorded for 11 f, except for H NMR (200 MHz, CDCl₃):

(100 MHz, CDCl₃): d=31.87, 29.65, 26.17, 22.63 ppm (CH₂alkyl chains);

IR (KBr disc): n˜ = 1759 (C=O), 2936, 2865, 1466, 1373, 1225, 1081,

758 cm^ꢀ1(C-O, C-H, C-C); MS (ES): m/z: calcd for: 760; found: 761

d=1.26 ppm (m, 66H, 33CH₂alkyl chains)and ¹³C NMR (50 MHz,

CDCl₃): d = 32.02, 29.81, 29.71, 29.63, 29.46, 26.30, 22.77 ppm (CH₂alkyl

Chem. Eur. J. 2007, 13, 5585 – 5600

ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemeurj.org

5595

P. Boullanger, J. W. Goodby et al.

[M+H]⁺, 731, 702, 666, 601, 566, 514, 514, 486, 460, 427, 395, 370, 330,

313, 296, 271, 243, 210, 197, 168, 144, 126, 97, 69.

cooled to 08C with stirring. A solution of TMSOTf (30 mL, 0.166 mmol)

in CH₂Cl₂(0.5 mL)was added dropwise over 1 h and the mixture was

stirred overnight at 08C. After filtration on Celite, and addition of

CH₂Cl₂(50 mL), the organic phase was washed with saturated aq

NaHCO₃, dried and concentrated to afford the crude product which was

purified by column chromatography.

O-(2,3,4,6-Tetra-O-acetyl-b-d-galactopyranosyl)-tri-O-nonyl pentaerythri-

tol (12c): Prepared from the alcohol 2c in 62% yield (Method C)after

purification by column chromatography. Oil; homogeneous by TLC, R_f=

0.56; [a]_D=ꢀ7.08 (c = 1.0, CHCl₃); ¹H and ¹³C NMR spectra were simi-

1

lar to those recorded for 12a, except for H NMR (400 MHz, CDCl₃): d

Bis-O-(2,3,4,6-tetra-O-benzoyl-b-d-galactopyranosyl)-di-O-hexyl pentaer-

ythritol (13a): Prepared in 72% yield from 5a; the crude product was pu-

rified twice by column chromatography (CH₂Cl₂/EtOH 99:1, then

EtOAc/petroleum ether 1:2). Oily material; R_f=0.63 (EtOAc/petroleum

ether 1:2); [a]_D=+46.78 (c = 1.0, CHCl₃); ¹H NMR (200 MHz, CDCl₃):

d=8.20–7.09 (m, 40H, 8C₆H₅CO), 5.91 (brd, 2H, J_3,4=3.4, J_4,5=0.5 Hz,

2H-4), 5.68 (brd, 2H, J_1,2=7.8, J_2,3=10.4 Hz, 2H-2), 5.41 (dd, 2H, 2H-3),

=

1.27 ppm (m, 36H, 18CH₂alkyl chains)and ¹³C NMR (100 MHz,

CDCl₃): d=31.92, 29.69, 29.65, 29.54, 29.35, 26.25, 22.70 ppm (CH₂alkyl

chains); IR (KBr disc): n˜ = 1758 (C=O), 2933, 2863, 1561, 1464, 1373,

1225, 1083 cm^ꢀ1(C-O, C-H, C-C); MS (ES): m/z: calcd for: 844; found:

846 [M+2]⁺, 702, 610, 556, 528, 498, 468, 443, 413, 383, 369, 352, 331, 325,

299, 289, 268, 250, 229, 225, 210, 197, 173, 169, 152, 139, 127, 109, 99, 85,

71.

4.54 (dd, 2H, J_5,6a=6.2, J_6a,6b=11.2 Hz, 2H-6a), 4.29 (dd, 2H, J_5,6b

=

7.1 Hz, 2H-6b), 4.06 (d, 2H, 2H-1), 3.93 (d, 2H, J=9.4 Hz, 2CH_aOC-1),

3.54 (m, 2H, 2H-5), 3.42–3.22 (m, 10H, 2CH₂OCH₂Alk, 2CH_bOC-1),

1.64 (m, 4H, 2OCH₂CH₂Alk), 1.26 (m, 12H, 6CH₂alkyl chains),

0.89 ppm (t, 6H, 2CH₃alkyl chains); ¹³C NMR (50 MHz, CDCl₃): d=

165.95, 165.66, 165.59, 164.94 (COC₆H₅), 133.62, 133.35, 130.07–128.37

(C₆H₅), 102.05 (C-1), 71.54 (OCH₂Alk), 71.25 (C-3), 70.92 (C-5), 70.15

O-(2,3,4,6-Tetra-O-acetyl-b-d-galactopyranosyl)-tri-O-decyl pentaerythri-

tol (12d): Prepared from the alcohol 2d in 53% yield (Method C)after

purification by column chromatography. Oil; homogeneous by TLC, R_f=

0.59; [a]_D=ꢀ8.08 (c = 1.0, CHCl₃); ¹H and ¹³C NMR spectra were simi-

1

lar to those recorded for 12a, except for H NMR (400 MHz, CDCl₃): d

=

1.26 ppm (m, 42H, 21CH₂alkyl chains)and ¹³C NMR (100 MHz,

(C-2), 69.17, 69.04 (CCH₂O), 68.06 (C-4), 61.71 (C-6), 45.24 (C(CH₂O)₄),

A

CDCl₃): d=31.92, 29.69, 29.63, 29.53, 29.36, 26.24, 22.69 ppm (CH₂alkyl

chains); IR (KBr disc): n˜ = 1759 (C=O), 2932, 2861, 1466, 1373, 1225,

1081, 758 cm^ꢀ1(C-O, C-H, C-C); MS (ES): m/z: calcd for: 909; found:

912, 911, 910 [M+Na+H⁺], 908, 844, 804, 784, 726, 698, 674, 596, 533,

504, 436, 392, 364, 334, 278.

31.74, 29.64, 25.90, 22.72 ppm (CH₂alkyl chains), 14.15 (CH₃alkyl

chains); elemental analysis calcd (%) for C ₈₅H₈₈O₂₂(1461.55): C 69.85, H

6.07; found: C 69.46, H 6.00.

Bis-O-(2,3,4,6-tetra-O-benzoyl-b-d-galactopyranosyl)-di-O-dodecyl pen-

taerythritol (13 f): Prepared in 45% yield from 5 f; the crude product was

purified twice by column chromatography (CH₂Cl₂/EtOH 99:1, then

EtOAc/petroleum ether 1:3). Oily material; R_f=0.62 (EtOAc/petroleum

ether 1:3); [a]_D=+54.08 (c = 1.0, CHCl₃); ¹H and ¹³C NMR spectra

were similar to those recorded for 13a except for ¹H NMR (200 MHz,

CDCl₃): d=1.26 ppm (m, 36H, 18CH₂alkyl chains)and ¹³C NMR

(200 MHz, CDCl₃): d = 32.00, 29.80, 29.64, 29.46, 26.32, 22.77 ppm (CH₂

alkyl chains); elemental analysis calcd (%) for C ₉₇H₁₁₂O₂₂(1629.87): C

71.48, H 6.93; found: C 71.61, H 7.24.

O-(2,3,4,6-Tetra-O-acetyl-b-d-galactopyranosyl)-tri-O-undecyl pentaery-

thritol (12e): Prepared from the alcohol 2e in 61% yield (Method C)

after purification by column chromatography. Oil; homogeneous by TLC,

R_f=0.62; [a]_D=ꢀ7.08 (c = 1.0, CHCl₃); ¹H and ¹³C NMR spectra were

similar to those recorded for 12a, except for ¹H NMR (400 MHz,

CDCl₃): d

=

1.26 ppm (m, 48H, 24CH₂alkyl chains)and ¹³C NMR

(100 MHz, CDCl₃): d=31.92, 29.69, 29.66, 29.54, 29.37, 26.25, 22.69 ppm

(CH₂alkyl chains); IR (KBr disc): n˜ = 1759 (C=O), 2932, 2861, 1466,

1372, 1224, 1081 cm^ꢀ1(C-O, C-H, C-C); MS (ES): m/z: calcd for: 951;

found: 952 [M+Na+H⁺], 911, 909, 805, 783, 765, 692, 670, 568, 510, 486,

436, 414, 351, 320, 243.

Bis-O-(2,3,4,6-tetra-O-benzoyl-b-d-galactopyranosyl)-di-O-tetradecyl

pentaerythritol (13g): Prepared in 62% yield from 5g; the crude product

was purified twice by column chromatography (CH₂Cl₂/EtOH 99:1, then

EtOAc/petroleum ether 1:3). Oily material; R_f=0.65 (EtOAc/petroleum

ether 1:3); [a]_D=+46.48 (c = 1.0, CHCl₃); ¹H and ¹³C NMR spectra

were similar to those recorded for 13 f except for ¹H NMR (200 MHz,

CDCl₃): d=1.26 ppm (m, 44H, 22CH₂alkyl chains); elemental analysis

calcd (%)for C ₁₀₁H₁₂₀O₂₂(1685.97): C 71.95, H 7.17; found: C 71.55, H

7.17.

O-(2,3,4,6-Tetra-O-acetyl-b-d-galactopyranosyl)-tri-O-dodecyl pentaery-

thritol (12 f): Prepared from the alcohol 2 f in 75% yield (Method A)or

53% yield (Method B)after purification by column chromatography

(ethyl acetate/petroleum ether 1:3)as an oily material. R_f=0.78; [a]_D=

ꢀ5.28 (c = 1.0, CHCl₃); ¹H and ¹³C NMR spectra were similar to those

recorded for 12a, except for ¹H NMR (200 MHz, CDCl₃): d=1.29 ppm

(m, 54H, 27CH₂alkyl chains)and ¹³C NMR (50 MHz, CDCl₃): d

=

31.91, 29.66, 29.50, 29.35, 26.24, 22.66 ppm (CH₂alkyl chains); elemental

analysis calcd (%)for C ₅₅H₁₀₂O₁₃(971.37): C 68.00, H 10.58; found: C

68.12, H 10.72.

Bis-O-(2,3,4,6-tetra-O-benzoyl-b-d-galactopyranosyl)-di-O-hexadecyl

pentaerythritol (13h): Prepared in 56% yield from 5h; the crude product

was purified twice by column chromatography (CH₂Cl₂/EtOH 99:1, then

EtOAc/petroleum ether 1:3). Oily material; R_f=0.67 (EtOAc/petroleum

ether 1:3); [a]_D=+52.48 (c = 1.0, CHCl₃);¹H and ¹³C NMR spectra were

similar to those recorded for 13 f except for H NMR (200 MHz, CDCl₃):

d=1.26 (m, 52H, 26CH₂alkyl chains); elemental analysis calcd (%) for

C₁₀₅H₁₂₈O₂₂(1742.07): C 72.38, H 7.40; found: C 72.13, H 7.28.

O-(2,3,4,6-Tetra-O-acetyl-b-d-galactopyranosyl)-tri-O-tetradecyl pentaer-

ythritol (12g): Prepared from the alcohol 2g in 82% yield (method A)

after purification by column chromatography (EtOAc/petroleum ether

1:4)as an oily material; R_f=0.72; [a]_D=ꢀ7.68 (c = 1.0, CHCl₃); ¹H and

¹³C NMR spectra were similar to those recorded for 12 f, except for

¹H NMR (200 MHz, CDCl₃): d=1.27 ppm (m, 66H, 33CH₂alkyl chains);

elemental analysis calcd (%)for C ₆₁H₁₁₄O₁₃(1055.52): C 69.41, H 10.88;

found: C 69.43, H 11.10.

1

General procedure for the preparation of bis-O-(2,3,4,6-tetra-O-acetyl-b-

d-galactopyranosyl)-di-O-alkyl pentaerythritol derivatives (14a,f–h)

Method A: Benzoyl derivative 13a,f–h (0.50 mmol)was treated overnight

O-(2,3,4,6-Tetra-O-acetyl-b-d-galactopyranosyl)-tri-O-hexadecyl pentaer-

ythritol (12h): Prepared from the alcohol 2h in 79% yield (method A)

or 35% yield (Method B)after purification by column chromatography

(EtOAc/petroleum ether 1:3)as an oily material; R_f=0.84 (ethyl acetate/

petroleum ether 1:3); [a]_D=ꢀ6.08 (c = 1.0, CHCl₃); ¹H and ¹³C NMR

spectra were similar to those recorded for 12 f, except for ¹H NMR

(200 MHz, CDCl₃): d=1.27 ppm (m, 78H, 39CH₂alkyl chains); elemen-

tal analysis calcd (%)for C ₆₇H₁₂₆O₁₃(1139.68): C 70.60, H 11.14; found:

C 70.65, H 11.33.

in MeOH containing a catalytic amount of sodium methylate (1—

5 mmol). After neutralization with Amberlyst IR 120 (H⁺), the solution

was concentrated and the residue was acetylated for 16 h in pyridine/

Ac₂O 2:1 (15 mL). After concentration the product was purified by

column chromatography affording compounds 14a,f–h in good yields.

Method B: A mixture of galactosyl bromide 9 (0.822 g, 2.00 mmol), ac-

ceptor alcohol (0.5 mmol)and crushed activated 4 molecular sieves

(0.8 g)in freshly distilled acetonitrile (8 mL)was stirred for 10 min under

argon. DDQ (0.220 g, 1.00 mmol)and iodine (0.504 g, 2.00 mmol)were

then added and the solution was stirred for 6 h at RT. After filtration and

concentration, the residue was dissolved in CH₂Cl₂(100 mL)and the or-

ganic phase was washed with saturated aq Na₂S₂O₃(225 mL), dried

(Na₂SO₄)and concentrated. The product was purified by column chroma-

tography.

General procedure for the preparation of di-O-alkyl-bis-O-(2,3,4,6-tetra-

O-benzoyl-b-d-galactopyranosyl) pentaerythritol derivatives (13a,f–h):

Compounds 5a,f–h (1.00 mmol)and trichloroacetimidate ( 8)^[14,37](1.50 g,

2.20 mmol)were dissolved in dry CH ₂Cl₂(6.0 mL)in the presence of

crushed activated 4 molecular sieves (0.5 g)and the suspension was

5596

www.chemeurj.org

ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Chem. Eur. J. 2007, 13, 5585 – 5600

O-Alkyl Pentaerythritol–Galactose Derivatives

FULL PAPER

Bis-O-(2,3,4,6-tetra-O-acetyl-b-d-galactopyranosyl)-di-O-hexyl pentaery-

thritol (14a): Obtained in 83% yield (method A)from 13a after purifica-

tion by column chromatography (EtOAc/petroleum ether 1:1)as an oily

material; R_f=0.30 (EtOAc/petroleum ether 2:3); [a]_D=ꢀ13.18 (c = 1.0,

165.03 (C₆H₅CO), 138.91, 133.64, 133.38, 131.09–127.31 (C₆H₅), 102.03

(C-1), 73.30 (CH₂C₆H₅), 71.65 (OCH₂Alk), 71.27 (C-3), 70.99 (C-5), 70.18

(C-2), 69.97 (C

N

31.99, 29.78, 29.64, 29.44, 26.28, 22.70 (CH₂alkyl chain), 14.28 ppm (CH₃

alkyl chain); elemental analysis calcd (%) for C ₉₂H₉₄O₂₂(1551.67): C

71.21, H 6.11; found: C 70.77, H 6.25.

CHCl₃); ¹H NMR (200 MHz, CDCl₃): d=5.39 (brd, 2H, J_3,4=3.2, J_4,5

=

0.5 Hz, 2H-4), 5.19 (brd, 2H, J_1,2=7.8, J_2,3=10.3 Hz, 2H-2), 4.99 (dd,

2H, 2H-3), 4.40 (d, 2H, 2H-1), 4.15 (m, 4H, 2H-6a, 2H-6b), 3.86 (dd,

2H, J_5,6a=6.1_,J_5,6b=7.1 Hz, 2H-5), 3.85 (d, 2H, J=9.4 Hz, 2CH_aOC-1),

3.43 (d, 2H, J=9.4 Hz, 2CH_bOC-1), 3.37–3.22 (m, 8H, 2CH₂OCH₂Alk),

2.14, 2.05, 2.03, 1.97 (4s, 24H, 8CH₃CO), 1.47 (m, 4H, 2OCH₂CH₂Alk),

1.28 (m, 12H, 6CH₂alkyl chains), 0.88 ppm (t, 6H, 2CH₃alkyl chains);

¹³C NMR (50 MHz, CDCl₃): d=170.29, 170.24, 170.07, 169.13 (CH₃CO),

101.85 (C-1), 71.53 (OCH₂Alk), 70.85 (C-3), 70.47 (C-5), 69.18 (CCH₂O),

Bis-O-(2,3,4,6-tetra-O-benzoyl-b-d-galactopyranosyl)-O-benzyl-O-hexa-

decyl pentaerythritol (15h): Prepared as described above and purified by

column chroamtography (EtOAc/petroleum ether 2:5). Product 15h was

obtained in 70% yield. Oily material; R_f=0.58 (EtOAc/petroleum ether

1:3); [a]_D=+48.08 (c

=

1.0, CHCl₃). ¹H NMR and ¹³C NMR spectra

were similar to those obtained for 15 f, except for ¹H NMR (200 MHz,

CDCl₃): d=1.26 ppm (m, 26H, 13CH₂alkyl chain); elemental analysis

calcd (%)for C ₉₆H₁₀₂O₂₂(1607.78): C 71.71, H 6.39; found: C 71.65, H

6.42.

69.13 (C-2), 68.78 (CCH₂O), 67.02 (C-4), 61.09 (C-6), 45.19 (C(CH₂O)₄),

A

31.63, 29.57, 25.85, 22.60 (CH₂alkyl chains), 14.02 ppm (CH₃alkyl

chains); elemental analysis calcd (%) for C ₄₅H₇₂O₂₂(965.03): C 56.00, H

7.52; found: C 56.22, H 7.49.

General procedure for the preparation of O-alkyl-bis-O-(2,3,4,6-tetra-O-

benzoyl-b-d-galactopyranosyl) pentaerythritol derivatives (16 f,h): 20%

Pd(OH)₂/C (100 mg)was added to compounds 15 f,h (0.65 mmol)in

EtOH (8 mL)and freshly distilled cyclohexene (4 mL, 39 mmol)and the

suspension was refluxed for 6 h. After filtration over Celite and concen-

tration, the residue was purified by column chromatography (EtOAc/pe-

troleum ether 1:2).

Bis-O-(2,3,4,6-tetra-O-acetyl-b-d-galactopyranosyl)-di-O-dodecyl

pen-

taerythritol (14 f): Obtained in 84% yield (method A)from 13 f after pu-

rification by column chromatography (EtOAc/petroleum ether 1:1). Oily

material; R_f=0.45 (EtOAc/petroleum ether 2:3); [a]_D=ꢀ12.7 (c = 1.0,

CHCl₃); ¹H NMR and ¹³C NMR spectra were similar to those recorded

for 14a except for ¹H NMR (200 MHz, CDCl₃): d=1.28 ppm (m, 36H,

18 CH₂alkyl chains); elemental analysis calcd (%) for C ₅₇H₉₆O₂₂

(1133.34): C 60.40, H 8.54; found: C 60.61, H 8.83.

Bis-O-(2,3,4,6-tetra-O-benzoyl-b-d-galactopyranosyl)-O-dodecyl pentaer-

ythritol (16 f): Prepared in 92% yield from 15 f. Oily material; R_f=0.66

(EtOAc/petroleum ether 1:2); [a]_D=+58.78 (c = 1.0, CHCl₃); ¹H NMR

(200 MHz, CDCl₃): d=8.09–7.21 (m, 40H, 8C₆H₅), 5.79 (m, 2H, 2H-4),

Bis-O-(2,3,4,6-tetra-O-acetyl-b-d-galactopyranosyl)-di-O-tetradecyl pen-

taerythritol (14g): Obtained from 13g in 85% yield (method A)or from

5g in 40% yield (method B), after purification by column chromatogra-

phy (EtOAc/petroleum ether 3:4). Oily material; R_f=0.67; [a]_D=ꢀ11.0

(c = 1.0, CHCl₃; ¹H NMR and ¹³C NMR spectra were similar to those re-

corded for 14 f except for ¹H NMR (200 MHz, CDCl₃): d=1.27 ppm (m,

44H, 22CH₂alkyl chains)and ¹³C NMR (50 MHz, CDCl₃): d = 31.84,

29.61, 29.44, 29.28, 26.18, 22.60 ppm (CH₂alkyl chains); elemental analy-

sis calcd (%)for C ₆₁H₁₀₄O₂₂(1189.44): C 61.59, H 8.81; found: C 61.54, H

8.92.

5.62 (dd, 2H, J_1,2=7.8, J_2,3=10.2 Hz, 2H-2), 5.39, 5.37 (2dd, 2H, J_3,4

=

3.4 Hz, 2H-3), 4.56, 4.50 (2 dd, J_5,6a=6.5, J_6a,6b=11.1 Hz, 2H-6a), 4.29

(dd, 2H, J_5,6b=6.5 Hz, 2H-6b), 3.93 (d, 2H, 2H-1), 3.87 (d, 2H, J=

9.5 Hz, 2CH_aOC-1), 3.74, 3.66 (2dd, 2H, J=11.5,

J_H,OH=6.4 Hz,

CH₂OH), 3.50 (m, 2H, H-5), 3.45–3.26 (m, 6H, 2CH_bOC-1,

CH₂OCH₂Alk), 2.66 (dd, 1H, CH₂OH), 1.44 (m, 2H, OCH₂CH₂Alk),

1.25 (m, 18H, 9CH₂alkyl chain), 0.89 ppm (t, 3H, CH₃alkyl chain);

¹³C NMR (200 MHz, CDCl₃): d=165.96, 165.65, 165.62, 165.54, 165.10,

165.05 (C₆H₅CO), 133.79, 133.67, 133.40, 130.05–128.38 (C₆H₅CO), 102.03

(C-1), 71.98 (OCH₂Alk), 71.08 (C-3), 70.95 (C-5), 70.07 (C-2), 69.64,

68.99 (CH₂OC-1, CH₂OAlk), 68.09, 67.94 (C-4), 65.31 (CH₂OH), 61.78

Bis-O-(2,3,4,6-tetra-O-acetyl-b-d-galactopyranosyl)-di-O-hexadecyl pen-

taerythritol (14h): Obtained from 13h in 86% yield (method A)after pu-

rification by column chromatography (EtOAc/petroleum ether 1:2). Oily

(C-6), 44.75 (C(CH₂O)₄), 31.96, 29.70, 29.54, 29.41, 26.15, 22.74 (CH₂

U

=

1.0, CHCl₃); ¹H NMR and

alkyl chain), 14.17 ppm (CH₃alkyl chain); elemental analysis calcd (%)

for C₈₅H₈₈O₂₂H₂O (1479.57): C 69.00, H 6.13; found: C 69.00, H 6.15.

material; R_f=0.69; [a]_D=ꢀ11.58 (c

¹³C NMR spectra were similar to those recorded for 14 f except for

¹H NMR (200 MHz, CDCl₃): d=1.27 ppm (m, 52H, 26CH₂alkyl chains);

elemental analysis calcd (%)for C ₆₅H₁₁₂O₂₂(1245.55): C 62.67, H 9.06;

found: C 62.36, H 9.25.

Bis-O-(2,3,4,6-tetra-O-benzoyl-b-d-galactopyranosyl)-O-hexadecyl pen-

taerythritol (16h): Prepared in 92% yield from 15h. Oily material; R_f=

0.70 (EtOAc/petroleum ether 1:2); [a]_D=+62.78 (c

= 1.0, CHCl₃);

¹H NMR and ¹³C NMR spectra were similar to those recorded for 16b

except for ¹H NMR (200 MHz, CDCl₃): d=1.25 ppm (m, 26H, 13CH₂

alkyl chain); elemental analysis calcd (%) for C ₈₉H₉₆O₂₂(1517.66): C

70.43, H 6.38; found: C 70.25, H 6.61.

General procedure for the preparation of O-alkyl-bis-O-(2,3,4,6-tetra-O-

benzoyl-b-d-galactopyranosyl)-O-benzyl

pentaerythritol

derivatives

(15 f,h): Compounds 7 f,h (1.00 mmol)and trichloroacetimidate 8 (1.50 g,

2.20 mmol)were dissolved in dry CH ₂Cl₂(6.0 mL)in the presence of

crushed activated 4 molecular sieves (0.8 g)and the suspension was

cooled to 08C with stirring. A solution of TMSOTf (30 mL, 0.166 mmol)

in CH₂Cl₂(0.5 mL)was added dropwise over 1 h and the mixture was

stirred overnight at 08C. After filtration on Celite, and addition of

CH₂Cl₂(50 mL), the organic phase was washed with saturated aq

NaHCO₃, dried and concentrated to afford the crude product which was

purified twice by column chromatography, first with MeOH/CHCl₃1:300,

then with different mixtures EtOAc/petroleum ether.

General procedure for the preparation of tris-O-(2,3,4,6-tetra-O-benzoyl-

b-d-galactopyranosyl)-O-alkyl pentaerythritol derivatives (17 f,h): Com-

pounds 16 f,h (0.50 mmol)and trichloroacetimidate

8

(0.407 g,

0.55 mmol)were dissolved in dry CH ₂Cl₂(5.0 mL)in the presence of

crushed activated 4 molecular sieves (0.4 g)and the suspension was

cooled to 08C with stirring. A solution of TMSOTf (20 mL, 0.11 mmol)in

CH₂Cl₂(0.5 mL)was added dropwise over 1 h and the mixture was stir-

red overnight at 08C. After filtration on Celite, the solution was directly

concentrated to afford the crude product which was purified by column

chromatography.

Bis-O-(2,3,4,6-tetra-O-benzoyl-b-d-galactopyranosyl)-O-benzyl-O-dode-

cyl pentaerythritol (15 f): Prepared as described above and purified by

column chromatography (EtOAc/petroleum ether 2:5). Product 15 f was

obtained in 72% yield as an oily material; R_f=0.54 (EtOAc/petroleum

ether 1:3); [a]_D=+50.58 (c = 1.0, CHCl₃); ¹H NMR (200 MHz, CDCl₃):

d=8.08–7.21 (m, 45H, 9C₆H₅), 5.80 (brd, 2H, J_3,4=3.4, J_4,5=0.5 Hz, 2H-

4), 5.64 (dd, 2H, J_1,2=7.8, J_2,3=10.3 Hz, 2H-2), 5.39 (dd, 2H, 2H-3), 4.54,

4.53 (2dd, J_5,6a=6.3, J_6a,6b=11.2 Hz, 2 H-6a), 4.39 (d, 2H, CH₂C₆H₅), 4.29

(d, 2H, J_5,6b=7.1 Hz, 2H-6b), 4.05 (d, 2H, 2H-1), 3.97, 3.96 (2d, 2H,

2CH_aOC-1), 3.53 (m, 4H, 2H-5, 2CH_bOC-1), 3.43, 3.39 (2d, 2H, J=

5.9 Hz, CH₂OCH₂C₆H₅), 3.34–3.20 (m, 4H, CH₂OCH₂Alk), 1.43 (m, 2H,

OCH₂CH₂Alk), 1.26 (m, 18H, 9CH₂alkyl chain), 0.88 ppm (t, 3H, CH₃

alkyl chain); ¹³C NMR (50 MHz, CDCl₃): d=165.97, 165.68, 165.61,

Tris-O-(2,3,4,6-tetra-O-benzoyl-b-d-galactopyranosyl)-O-dodecyl pentaer-

ythritol (17 f): Prepared as described above in 68% yield, after purifica-

tion by column chromatography (MeOH/CHCl₃1:175, then EtOAc/pe-

troleum ether 1:2). Amorphous solid; R_f=0.58 (EtOAc/petroleum ether

1:2); [a]_D=+55.08 (c = 1.0, CHCl₃); ¹H NMR (200 MHz, CDCl₃): d=

8.09–7.21 (m, 60H, 12C₆H₅), 5.82 (brd, 3H, J_3,4=3.3, J_4,5=0.5 Hz, 3H-4),

5.65 (dd, 3H, J_1,2=7.8, J_2,3=10.4 Hz, 3H-2), 5.39 (dd, 3H, 3H-3), 4.52

(dd, J_5,6a=6.2, J_6a,6b=11.1 Hz, 3H-6a), 4.29 (dd, 3H, J_5,6b=6.4 Hz, 3H-

6b), 4.08 (d, 3H, 3H-1), 3.92 (d, 3H, J=9.5 Hz, 3CH_aOC-1), 3.52 (m,

3H, 3H-5), 3.39–3.20 (m, 7H, 3CH_bOC-1, CH₂OCH₂Alk), 1.44 (m, 2H,

OCH₂CH₂Alk), 1.22 (m, 18H, 9CH₂alkyl chain), 0.87 ppm (t, 3H, CH₃

Chem. Eur. J. 2007, 13, 5585 – 5600

ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemeurj.org

5597

P. Boullanger, J. W. Goodby et al.

alkyl chain); ¹³C NMR (50 MHz, CDCl₃): d=165.92, 165.69, 165.60,

165.02 (C₆H₅CO), 133.96, 133.64, 133.43, 130.08–128.39 (C₆H₅), 101.94

(C-1), 71.71 (OCH₂Alk), 71.38 (C-3), 70.96 (C-5), 70.28 (C-2), 68.34 (C-

nol added (150 mL)and the solvent concentrated to yield a white solid

which was removed by filtration.

O-b-d-Galactopyranosyl-tri-O-hexyl pentaerythritol (19a): Prepared

from 12a in 93% yield as described in Method A. Oily material; [a]_D=

ꢀ9.58 (c = 1.0, CHCl₃); ¹H NMR (200 MHz, CDCl₃): d = 4.22 (dd, 1H,

A

N

29.68, 29.44, 26.31, 22.76 (CH₂alkyl chain), 14.22 ppm (CH₃alkyl chain);

elemental analysis calcd (%)for C ₁₁₉H₁₁₄O₃₁(2040.10): C 70.05, H 5.63;

found: C 70.09, H 5.56.

J

_1,2=7.0 Hz, H-1), 3.99–3.35 (m, 20H, H-2, H-3, H-4, H-5, H-6a, H-6b,

CH₂OC-1, 3CH₂OCH₂Alk), 1.53 (m, 6H, 3OCH₂CH₂Alk), 1.29 (m, 18H,

9CH₂alkyl chains), 0.89 ppm (t, 9H, 3CH₃alkyl chains); ¹³C NMR

(50 MHz, CDCl₃): d=104.70 (C-1), 74.71 (C-5), 73.45 (C-3), 71.68

(OCH₂Alk), 71.31 (C-2), 70.33 (CH₂OC-1), 69.52 (CH₂OAlk), 68.55 (C-

Tris-O-(2,3,4,6-tetra-O-benzoyl-b-d-galactopyranosyl)-O-hexadecyl pen-

taerythritol (17h): Prepared as described above in 73% yield, after pu-

rification by column chromatography (MeOH/CHCl₃1:300, then EtOAc/

petroleum ether 1:2). Amorphous solid; R_f=0.62 (EtOAc/petroleum

ether 1:2); [a]_D=+44.38 (c = 1.0, CHCl₃); ¹H and ¹³C NMR spectra

were similar to those recorded for 17 f except for ¹H NMR (200 MHz,

CDCl₃): d=1.23 ppm (m, 26H, 13CH₂alkyl chain); elemental analysis

calcd (%)for C ₁₂₃H₁₂₂O₃₁(2096.21): C 70.47, H 5.87; found: C 70.17, H

5.81.

4), 60.92 (C-6), 45.47 (C(CH₂O)₄), 31.70, 29.55, 25.86, 22.65 (CH₂alkyl

G

chains), 14.03 ppm (CH₃alkyl chains); elemental analysis calcd (%) for

C₂₉H₅₈O₉H₂O (568.77): C 61.26, H 10.63; found: C 61.36, H 10.50.

O-b-d-Galactopyranosyl-tri-O-heptyl pentaerythritol (19b): Prepared

from 12b in 40% yield as described Method B. Oil; [a]_D=ꢀ7.58 (c =

1.0, CHCl₃); ¹H and ¹³C NMR spectra were similar to those recorded for

19c (see below)except for

1.25 ppm (m, 24H, 12CH₂alkyl chains)and

[D₆]DMSO): d=31.30, 29.07, 28.49, 25.66, 22.03 ppm (CH₂alkyl chains);

¹H NMR (400 MHz, [D₆]DMSO): d=

¹³C NMR (100 MHz,

General procedure for the preparation of tris-O-(2,3,4,6-tetra-O-acetyl-b-

d-galactopyranosyl)-O-alkyl pentaerythritol derivatives (18 f,h): Com-

pounds 17 f,h (0.30 mmol)were treated overnight in MeOH (50 mL)con-

taining a catalytic amount of sodium (1–3 mmol). After neutralization of

the solution with Amberlyst IR 120 [H⁺], filtration and concentration,

the residue was washed with petroleum ether (220 mL); the superna-

tant was removed and the product was acetylated overnight in Ac₂O/pyri-

dine 1:2 (15 mL). After a new concentration, the pure compound was re-

covered after purification by column chromatography.

IR (KBr disc): n˜

= 3418 (OH), 2934, 2864, 1660, 1467, 1376, 1302,

1101 cm^ꢀ1(C-O, C-H, C-C); MS (ES): m/z: calcd for: 593; found: 593

[M]⁺, 561, 472, 459, 446, 431, 413, 396, 394, 369, 360, 352, 333, 315, 299,

296, 243, 229, 217, 201, 197, 182, 169, 145, 133, 127, 113, 99, 83, 71.

O-b-d-Galactopyranosyl-tri-O-nonyl pentaerythritol (19c): Prepared

from 12c in 60% yield as described Method B. Oil; [a]_D=ꢀ6.58 (c =

1.0, CHCl₃); ¹H and ¹³C NMR spectra showed no peaks additional to

those interpreted for the target compound. They are shown as Supporting

Information in Figures S14 and S15, together with the COSY (Fig-

Tris-O-(2,3,4,6-tetra-O-acetyl-b-d-galactopyranosyl)-O-dodecyl pentaery-

thritol (18 f): Prepared as described above in 71% yield, after purifica-

tion by column chromatography (EtOAc/petroleum ether 3:2). Oily ma-

ure S16)and HMQC (Figure S17)2-D spectra.

¹H NMR (300 MHz,

terial; R_f=0.69; [a]_D=ꢀ15.78 (c

CDCl₃): d=5.39 (brd, 3H, J_3,4=3.3, J_4,5=0.5 Hz, 3H-4), 5.17 (dd, 3H,

_1,2=7.8, J_2,3=10.4 Hz, 3H-2), 5.02 (dd, 3H, 3H-3), 4.39 (d, 3H, 3H-1),

=

1.0, CHCl₃); ¹H NMR (200 MHz,

[D₆]DMSO): d=4.72 (d, 1H, J_2,OH=4 Hz, OH-2), 4.66 (d, 1H, J_3,OH

5 Hz, OH-3), 4.53 (t, 1H, J_6,OH=5.0 Hz, OH-6), 4.33 (d, 1H, J_4,OH

=

J

4.0 Hz, OH-4), 3.96 (d, 1H, J=7.0 Hz, H-1), 3.66 (d, 1H, J_gem=10.0 Hz,

CH_aOC-1), 3.61 (m, 1H, H-4), 3.52 (m, 1H, H-6a), 3.46 (m, 1H, H-6’),

3.34–3.18 (m, 16H, CH_bOC-1, 3CH₂OCH₂Alk, H-2, H-3, H-5), 1.45 (m,

6H, 3OCH₂CH₂Alk), 1.23 (m, 36H, 18CH₂alkyl chains), 0.84 ppm (t,

9H, 3CH₃alkyl chains); ¹³C NMR (75 MHz, [D₆]DMSO): d=104.76 (C-

1), 75.12 (C-5), 73.35 (C-3), 70.65 (C-2), 70.54 (OCH₂Alk), 68.73

(CH₂OAlk), 68.32 (CH₂OC-1), 68.02 (C-4), 60.24 (C-6), 45.05 (C-

4.16 (d, 6H, J_5,6a=J_5,6b=6.7 Hz, 3H-6a, 3H-6b), 3.90 (brt, 3H, 3H-5),

3.83 (d, 3H, J=9.8 Hz, 3CH_aOC-1), 3.42 (d, 3H, J=9.8 Hz, 3CH_bOC-1),

3.40–3.20 (m, 4H, CH₂OCH₂Alk), 2.17, 2.07, 2.05, 1.99 (4s, 36H,

12CH₃CO), 1.52 (m, 2H, OCH₂CH₂Alk), 1.26 (m, 18H, 9CH₂alkyl

chain), 0.88 ppm (t, 3H, CH₃alkyl chain); ¹³C NMR (50 MHz, CDCl₃):

d=170.21, 170.18, 169.98, 169.09 (CH₃CO), 101.72 (C-1), 71.64

(OCH₂Alk), 70.73, 70.52 (C-3, C-5), 69.16 (C-2), 68.73 (CH₂OC-1), 68.33

A

(CH₂OAlk), 66.96 (C-4), 60.99 (C-6), 45.08 (C(CH₂O)₄), 31.94, 29.65,

T

13.91 ppm (CH₃alkyl chains); IR (KBr disc): n˜

= 3409 (OH), 2935,

29.48, 29.28, 26.19, 22.65 (CH₂alkyl chain), 14.15 ppm (CH₃alkyl chain);

elemental analysis calcd (%)for C ₅₉H₉₀O₃₁(1295.31): C 54.70, H 7.00;

found: C 54.27, H 6.88.

2860, 1466, 1376, 1078 cm^ꢀ1(C-O, C-H, C-C); MS (ES): m/z: calcd for:

677; found: 677 [M]⁺, 516, 299, 250, 237, 180, 164, 150, 137, 121, 91, 85,

71.

Tris-O-(2,3,4,6-tetra-O-acetyl-b-d-galactopyranosyl)-O-hexdecyl pentaer-

ythritol (18h): Prepared as described above in 73% yield, after purifica-

tion by column chromatography (EtOAc/petroleum ether 4:3). Oily ma-

Tri-O-decyl-O-b-d-galactopyranosyl pentaerythritol (19d): Prepared

from 12d in 88% yield as described Method B. Oil; [a]_D=ꢀ6.08 (c =

1.0, CHCl₃); ¹H and ¹³C NMR spectra were similar to those recorded for

terial; R_f=0.71 (EtOAc/petroleum ether 3:2); [a]_D=ꢀ19.28 (c

= 1.0,

19c (see below)except for

1.23 ppm (m, 42H, 21CH₂alkyl chains)and

¹H NMR (400 MHz, [D₆]DMSO): d=

¹³C NMR (100 MHz,

CHCl₃); ¹H NMR and ¹³C NMR were similar to those recorded for 18 f,

except for ¹H NMR (200 MHz, CDCl₃): d=1.25 ppm (m, 26H, 13CH₂

alkyl chain); elemental analysis calcd (%) for C ₆₃H₉₈O₃₁(1351.41): C

55.99, H 7.31; found: C 55.86, H 7.43.

[D₆]DMSO): d=31.30, 29.09, 29.05, 28.98, 28.83, 25.72, 25.70, 22.08 ppm

(CH₂alkyl chains); IR (KBr disc): n˜ = 3394 (OH), 2929, 1649, 1466,

1377, 1304, 1080, 915, 721 cm^ꢀ1(C-O, C-H, C-C); MS (ES): m/z: calcd

for: 719; found: 719 [M]⁺, 558, 516, 418, 402, 380, 352, 327, 299, 259, 254,

240, 224, 211, 187, 173, 163, 145, 141, 127, 110, 91, 85, 71.

General procedure for de-O-acetylation of the pentaerythritol derivatives

12a–h, 14a,f–h and 18 f,h

Method A: Compounds 12a,f–h (1.00 mmol), 14a,f–h (0.50 mmol)or

18 f,h (0.20 mmol)were treated overnight in MeOH (50 mL)containing a

catalytic amount of sodium (1 mol%). The pure product was directly ob-

tained after neutralization of the solution with Amberlyst IR 120 [H⁺],

filtration and concentration.

O-b-d-Galactopyranosyl-tri-O-undecyl pentaerythritol (19e): Prepared

from 12e in 67% yield as described Method B. Oil; [a]_D=ꢀ5.58 (c =

1.0, CHCl₃); ¹H and ¹³C NMR spectra showed no peaks additional to

those interpreted for the target compound. ¹H and ¹³C NMR spectra

were similar to those recorded for 19c (see below)except for ¹H NMR

(400 MHz, [D₆]DMSO): d=1.23 ppm (m, 48H, 24CH₂alkyl chains)and

¹³C NMR (100 MHz, [D₆]DMSO): d=31.27, 29.06, 29.00, 28.80, 28.70,

25.68, 22.06 ppm (CH₂alkyl chains); IR (KBr disc): n˜ = 3422 (OH),

2929, 2859, 2336, 1619, 1464, 1068 cm^ꢀ1(C-O, C-H, C-C); MS (ES): m/z:

calcd for: 761; found: 761 [M]⁺, 600, 432, 416, 395, 355, 339, 315, 296,

269, 254, 225, 198, 182, 169, 145, 133, 119, 113, 99, 85, 71.

Method B: A solution of 1m sodium methoxide in MeOH (1 mL)was

added to a solution of the respective protected derivative 12b–e (1.02 g,

1.3 mmol)in anhydrous MeOH (18 mL)and anhydrous CH ₂Cl₂(12 mL).

The resulting mixture was stirred at room temperature for 15 min under

nitrogen. The solvent was removed, water (20 mL)and methanol (5 mL)

added and the subsequent solution stirred overnight at room tempera-

ture. The reaction mixture was neutralized with Amberlyst IR-120 [H⁺]

filtered and the resin washed with EtOH (20 mL). The solvent was re-

moved to yield an off white solid which was partitioned between with bu-

tanol (60 mL)and water (40 mL). The organic layer was separated, etha-

Tri-O-dodecyl-O-b-d-galactopyranosyl pentaerythritol (19 f): Prepared

from 12 f in 90% yield as described in Method A. Oily material; [a]_D=

ꢀ5.28 (c = 1.0, CHCl₃); ¹H NMR and ¹³C NMR spectra were similar to

those recorded for 19a, except for ¹H NMR (200 MHz, CDCl₃): d=

5598

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ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Chem. Eur. J. 2007, 13, 5585 – 5600

O-Alkyl Pentaerythritol–Galactose Derivatives

FULL PAPER

1.29 ppm (m, 54H, 27CH₂alkyl chains)and ¹³C NMR (50 MHz, CDCl₃):

d=31.97, 29.77, 29.73, 29.63, 29.60, 29.42, 26.24, 22.76 ppm (CH₂alkyl

chains); elemental analysis calcd (%) for C ₄₇H₉₄O₉2H₂O (839.34): C

67.25, H 11.77; found: C 67.48, H 11.43.

Tri-O-b-d-galactopyranosyl O-hexadecyl pentaerythritol (21h): Prepared

from 18h in 95% yield as described in Method A. White solid; [a]_D=

ꢀ9.48 (c = 1.0, MeOH); ¹NMR and ¹³C NMR spectra were similar to

those reported for 21 f except for ¹H NMR (200 MHz, CD₃OD): d=

1.30 ppm (m, 26H, 13CH₂alkyl chain); elemental analysis calcd (%) for

C₃₉H₇₄O₁₉2H₂O (883.01): C 53.04, H 8.90; found: C 53.00, H 8.86.

O-b-d-Galactopyranosyl-tri-O-tetradecyl pentaerythritol (19g): Prepared

from 12g in 95% yield as described in Method A. White solid; m.p. 77–

788C (MeOH); [a]_D=ꢀ4.68 (c = 1.0, CHCl₃); ¹H NMR and ¹³C NMR

spectra were similar to those recorded for 19a, except for ¹H NMR

(200 MHz, CDCl₃): d=1.26 ppm (m, 66H, 33CH₂alkyl chains); elemen-

tal analysis calcd (%)for C ₅₃H₁₀₆O₉2H₂O (923.41): C 68.93, H 12.00;

found: C 68.76, H 11.61.

Acknowledgements

We thank M.-N. Bouchu for technical assistance, the Centre National de

la Recherche Scientifique and the French Minister of Foreign Office, the

Ramsay Memorial Fund and the Engineering and Physical Sciences Re-

search Council (EPSRC)for financial support.

O-b-d-Galactopyranosyl-tri-O-hexadecyl pentaerythritol (19h): Prepared

from 12h in 93% yield as described in Method A. White solid; mp 87–

888C (MeOH); [a]_D=ꢀ5.08 (c = 1.0, CHCl₃); ¹H NMR and ¹³C NMR

spectra were similar to those recorded for 19a, except for ¹H NMR

(200 MHz, CDCl₃): d=1.26 ppm (m, 78H, 39CH₂alkyl chains); elemen-

tal analysis calcd (%)for C ₅₉H₁₁₈O₉2H₂O (1007.57): C 70.33, H 12.21;

found: C 70.22, H 12.36.

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Di-O-b-d-galactopyranosyl-di-O-hexyl pentaerythritol (20a): Prepared

from 14a in 95% yield as described in Method A. Amorphous solid;

[a]_D=ꢀ11.68 (c = 1.0, CH₃OH); ¹H NMR (200 MHz, CD₃OD): d=4.25

(d, 2H, J_1,2=7.0 Hz, 2H-1), 3.93 (d, 2H, J=9.9 Hz, 2CH_aOC-1), 3.83 (d,

2H, J_3,4=3.4, J_4,5=0.6 Hz, 2H-4), 3.74 (m, 4H, 2H-6a, 2H-6b), 3.61 (d,

2H, J=9.9 Hz, 2CH_bOC-1), 3.52 (dd, 2H, J_2,3=9.9 Hz, 2H-2), 3.50–3.42

(m, 8H, 2H-3, 2H-5, 2CH₂OAlk), 3.40 (t, 4H, J=6.3 Hz, 2OCH₂CH₂),

1.54 (m, 4H, 2OCH₂CH₂Alk), 1.31 (m, 12H, 6CH₂alkyl chains),

0.91 ppm (t, 6H, 2CH₃alkyl chains); ¹³C NMR (50 MHz, CD₃OD): d=

106.01 (C-1), 76.76 (C-5), 75.29 (C-3), 72.95 (C-2), 72.88 (OCH₂CH₂Alk),

70.85, 70.44 (OCH₂Alk, OCH₂C-1), 70.52 (C-4), 62.61 (C-6), 46.82 (C-

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Di-O-dodecyl-di-O-b-d-galactopyranosyl pentaerythritol (20 f): Com-

pound 20 f was prepared from 14 f in 91% yield as described in Method

A. Amorphous solid; [a]_D=ꢀ7.28 (c

=

1.0, CH₃OH); ¹H NMR and

¹³C NMR spectra were similar to those recorded for 20a, except for

¹H NMR (200 MHz, CD₃OD): d=1.31 ppm (m, 36H, 18CH₂alkyl

chains)and ¹³C NMR (50 MHz, CD₃OD): d=33.38, 31.14, 31.09, 30.96,

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Di-O-b-d-galactopyranosyl-di-O-tetradecyl pentaerythritol (20g): Com-

pound 20g was prepared from 14g in 92% yield as described in Method

A. Amorphous solid; [a]_D=ꢀ5.28 (c

¹³C NMR spectra were similar to those recorded for 20 f, except for

¹H NMR (200 MHz, CD₃OD): d

1.29 ppm (m, 44H, 22CH₂alkyl

=

1.0, CH₃OH); ¹H NMR and

=

chains); elemental analysis calcd (%) for C ₄₅H₈₈O₁₄2H₂O (889.19): C

60.78, H 10.42; found: C 60.79, H 10.13.

Di-O-b-d-galactopyranosyl-di-O-hexadecyl pentaerythritol (20h): Com-

pound 20h was prepared from 14h in 92% yield as described in Method

A. Amorphous solid; [a]_D=ꢀ8.48 (c

=

1.0, MeOH); ¹H NMR and

¹³C NMR spectra were similar to those recorded for 20 f except for

¹H NMR (200 MHz, CD₃OD): d=1.30 ppm (m, 52H, 26CH₂alkyl

chains); elemental analysis calcd (%) for C ₄₉H₉₆O₁₄1.5H₂O (936.28): C

62.85, H 10.66; found: C 62.73, H 10.54.

O-Dodecyl-tri-O-b-d-galactopyranosyl pentaerythritol (21 f): Prepared

from 18 f in 92% yield as described in Method A. White solid; [a]_D=

ꢀ10.68 (c = 1.0, MeOH); ¹H NMR (200 MHz, CD₃OD): d=4.27 (d, 3H,

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Chem. Eur. J. 2007, 13, 5585 – 5600

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Received: November 28, 2006

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Published online: February 20, 2007

5600

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Chem. Eur. J. 2007, 13, 5585 – 5600

Article Doi

Synthesis and liquid crystalline properties of mono-, di- and tri-O-alkyl pentaerythritol derivatives bearing tri-, di- or monogalactosyl heads: The effects of curvature of molecular packing on mesophase formation

DOI: 10.1002/chem.200601702

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