Synthesis and application of carbohydrate-derived morpholine amino acids

Article abstract of DOI:10.1021/jo048630x

The synthesis of series of diversely functionalized ε-morpholine amino acids (MAAs, 5a-h) starting from an ε-sugar amino acid and following a two-step oxidative glycol cleavage/reductive amination strategy, is described. In an alternative synthetic scheme

Full text of DOI:10.1021/jo048630x

Synthesis and Application of Carbohydrate-Derived
Morpholine Amino Acids†
Gijsbert M. Grotenbreg, Alphert E. Christina, Annelies E. M. Buizert,
Gijsbert A. van der Marel, Herman S. Overkleeft, and Mark Overhand*
Leiden Institute of Chemistry, Gorlaeus Laboratories, P.O. Box 9502, 2300 RA Leiden, The Netherlands
overhand@chem.leidenuniv.nl
Received August 6, 2004
The synthesis of series of diversely functionalized ꢀ-morpholine amino acids (MAAs, 5a-h) starting
from an ꢀ-sugar amino acid and following a two-step oxidative glycol cleavage/reductive amination
strategy, is described. In an alternative synthetic scheme, diastereoisomerically pure δ-MAAs (12a,b)
were obtained. Oligopeptides containing MAAs were prepared either by direct incorporation of a
MAA building block or by subjecting a fully assembled SAA-containing peptide to the two-step
glycol cleavage/reductive amination procedure.
Introduction
For example, in a recent contribution from our laboratory
we revealed that the incorporation of a furanoid SAA into
the turn region of gramicidin S (GS) induces an unusual
turn structure with a hydroxyl protruding into the turn
region of GS causing a disruption in the H-bonding
pattern as compared to the native peptide.6 The free
hydroxyl functionalities in SAAs can also be equipped
with pharmacophores, thereby increasing their resem-
blance with native peptide sequences. This principle was
elegantly demonstrated by Smith et al. in the synthesis
of a potential mammalian ribonuclease reductase inhibi-
tor.7 In this example, a tetrahydropyran scaffold was
adorned with a methylene carboxylate and an isobutyl
group that mimic the aspartic acid and leucine side
chains, respectively. Next to the decoration of the hy-
droxyls, another type of derivatization can be envisaged
based on oxidative glycol-cleavage of a 1,2-diol function-
ality on the furan or pyran core structure. The ring
structure can subsequently be reinstalled by double-
reductive amination of the resulting dialdehyde, resulting
in a substituted morpholine. Previously, Du et al. re-
ported the synthesis of morpholinoglycopeptides starting
from glycopyranosides.8a Inositol triphosphate analogues
having substituted amines introduced into the carbacyclic
core have been prepared by Malmberg et al.8b Further-
The design, synthesis, and application of peptidomi-
metic compounds has been a focal point of research for
many years. The generation of a plethora of peptide ana-
logues and their incorporation in oligopeptides has led
to the identification of pharmaceutically interesting
compounds.1 As secondary structure is a decisive factor
in the functioning of peptides and proteins, scaffolds that
restrict the conformational freedom have been applied
to provide structural stabilization when incorporated in
oligopeptides.2 Moreover, the incorporation of nonproteino-
genic residues can have beneficial effects on metabolic
stability, whereas additional functionalities on the mo-
lecular framework allow the attachment of potential
pharmacophoric groups. Sugar amino acids (SAAs),
carbohydrate scaffolds appended with an amine and
carboxylic acid moiety, have been employed successfully
as nonproteinogenic compounds.3 SAAs are a structurally
and functionally diverse class of peptidomimetics and
exist as furanoid, pyranoid, open-chain,4 and fused-ring
systems.5 Hydroxyl groups that originate from the parent
sugar can participate in secondary structure formation.
* To whom correspondence should be addressed. Tel: +31(0)71-
5274483. Fax: +31(0)71-5274307.
† Dedicated to the memory of our colleague Jacques van Boom, who
passed away on July 31, 2004, at the age of 67.
(4) (a) Hunter, D. F. A.; Fleet, G. W. J. Tetrahedron: Asymmetry
2003, 14, 3831-3839. (b) Mayes, B. A.; Cowley, A. R.; Ansell, C. W.
G.; Fleet, G. W. J. Tetrahedron Lett. 2004, 45, 163-166. (c) Mayes, B.
A.; Simon, L.; Watkin, D. J.; Ansell, C. W. G.; Fleet, G. W. J.
Tetrahedron Lett., 2004, 45, 157-162. (d) Mayes, B. A.; Stetz, R. J.
E.; Ansell, C. W. G.; Fleet, G. W. J. Tetrahedron Lett., 2004, 45, 153-
156.
(1) (a) Synthesis of Peptides and Peptidomimetics. Houben-Weyl,
Methods in Organic Chemistry; Goodman, M., Felix, A., Moroder, L.,
Toniolo, C., Eds.; Thieme: Stuttgart, New York, 2003; Vol. E22c. (b)
Hanessian, S.; McNaughton-Smith, G.; Lombart, H.-G.; Lubell, W. D.
Tetrahedron 1997, 53, 12789-12854. (c) Gillespie, P.; Cicariello, J.;
Olson, G. L. Biopolym. (Peptide Sci.) 1997, 43, 191-217.
(2) (a) Hill, D. J.; Mio, M. J.; Prince, R. B.; Hughes, T. S.; Moore, J.
S. Chem. Rev. 2001, 101, 3893-4011. (b) Gellman, S. H. Acc. Chem.
Res. 1998, 31, 173-180. (c) Seebach, D.; Matthews, J. L. Chem.
Commun. 1997, 2015-2022. (d) Nowick, J. S.; Smith, E. M.; Pairish,
M. Chem. Soc. Rev. 1996, 25, 401-415. (e) Liskamp, R. M. J. Recl.
Trav. Chim. Pays-Bas 1994, 113, 1-19.
(3) For reviews on SAAs, see: (a) Chakraborty, T. K.; Srinivasu,
P.; Tapadar, S.; Mohan, B. K. J. Chem. Sci. 2004, 116, 187-207. (b)
Gervay-Hague, J.; Weathers, T. M. J. Carbohydr. Chem. 2002, 21,
867-910. (c) Gruner, S. A. W.; Locardi, E.; Lohof, E.; Kessler, H. Chem.
Rev. 2002, 102, 491-514. (d) Schweizer, F. Angew. Chem., Int. Ed.
2002, 41, 230-253. (e) Peri, F.; Cipolla, L.; Forni, E.; La Ferla, B.;
Nicotra, F. Chemtracts Org. Chem. 2001, 14, 481-499.
(5) (a) Peri, F.; Cipolla, L.; La Ferla, B.; Nicotra, F. Chem. Commun.
2000, 2303-2304. (b) van Well, R. M.; Meijer, M. E. A.; Overkleeft, H.
S.; van Boom, J. H.; van der Marel, G. A.; Overhand, M. Tetrahedron
2003, 59, 2423-2434. (c) Dondoni, A.; Marra, A.; Richichi, B. Synlett
2003, 2345-2348. (d) Grotenbreg, G. M.; Tuin, A. W.; Witte, M. D.;
Leeuwenburgh, M. A.; van Boom, J. H.; van der Marel, G. A.;
Overkleeft, H. S.; Overhand, M. Synlett 2004, 904-906.
(6) Grotenbreg, G. M.; Timmer, M. S. M.; Llamas-Saiz, A. L.;
Verdoes, M.; van der Marel, G. A.; van Raaij, M. J.; Overkleeft, H. S.;
Overhand, M. J. Am. Chem. Soc. 2004, 126, 3444-3446.
(7) Smith, A. B., III; Sasho, S.; Barwis, B. A.; Sprengeler, P.;
Barbosa, J.; Hirschmann, R.; Cooperman, B. S. Bioorg. Med. Chem.
Lett. 1998, 8, 3133-3136.
10.1021/jo048630x CCC: $27.50 © 2004 American Chemical Society
Published on Web 11/04/2004
J. Org. Chem. 2004, 69, 8331-8339
8331

Grotenbreg et al.
SCHEME 1a
a Reagents and conditions: (i) 2 M HCl/MeOH (1/3 v/v), 16 h, 82%; (ii) H5IO6 (1.5 equiv), THF, 20 min, 94%; (iii) R-NH2 (1.1 equiv),
NaCNBH3 (4.2 equiv), trimethyl orthoformate/MeOH (1/3 v/v), AcOH, 3 Å mol sieves, 16 h, 4a; 54%, 4b; 36%, 4c; 38%, 4d; 59%, 4e; 33%,
4f; 45%, 4g; 41% and 4h; 33%; (iv) 1 m NaOH (2 equiv), THF, 4 h, then Amberlite IR-120 (H+), 5a; quant, 5b; 94%, 5c; quant, 5d; quant,
5e; 78%, 5f; 45%, 5g; 78% and 5h; quant.
more, the generation of morpholine derivatives from
nucleoside building blocks and their incorporation in
oligonucleotide analogues that possess favorable anti-
sense properties has been described.9
system to give 2 in 82% yield. Glycol cleavage was
effected by treatment with periodic acid to afford dial-
dehyde 3, together with its corresponding hydrates.11 The
MAA-core structures 4a-h were obtained after slow
addition of a solution of the appropriate amine in MeOH,
that had been acidified with AcOH to approximately pH
) 5 in advance, to a mixture of 3 and NaCNBH3.12 The
yields of the double reductive aminations varied for the
benzylic amines (4a; 54%, 4b; 36%, 4c; 38%), the amino
acid derivatives (4d; 59%, 4e; 33%, 4f; 45%), and the
aliphatic amines (4g; 41%, 4h; 33%). Saponification of
the methyl ester functionalities in 4a-h produced the
free ꢀ-morpholine amino acids 5a-h.
To establish whether the above-described approach to
ꢀ-MAAs is also amenable for δ-MAAs, SAA 7 (Scheme
2), having a similar cis-diol system as template 2, was
selected as our next synthetic target. The appropriate
precursor 6 was prepared in a five-step procedure,
comprising Kiliani ascension13 of cyclohexylidene-pro-
tected D-(+)-ribose, followed by ditosylation, base-cata-
lyzed ring contraction and introduction of the azide,
according to the procedure developed by Fleet and co-
workers.14 The cis-diol in 7 was unveiled by acidic release
of the cyclohexylidene group in 6 (59%). Periodate oxida-
We herein report the synthesis of a series δ- and
ꢀ-morpholine amino acids (MAAs) bearing several differ-
ent moieties on the endocyclic nitrogen, starting from
SAA building blocks and following the aforementioned
glycol-cleavage/reductive amination-strategy. To demon-
strate the versatility of the approach, a single type II′
â-turn of the model peptide GS has been replaced by an
ꢀ-MAA, both through direct incorporation of an MAA
building block and by modification of a SAA-containing
GS analogue after complete assembly of the cyclic oli-
gopeptide.
Results and Discussion
The synthesis of a set of ꢀ-morpholine amino acids (5a-
h) is outlined in Scheme 1. Starting from D-(+)-ribose,
the protected SAA building block 1 was obtained follow-
ing a high-yielding four-step procedure developed re-
cently in our laboratory.10 This route entails the instal-
lation of the acetonide at the 2,3-diol, Wittig olefination
at the anomeric center, mesylation of the remaining
hydroxyl functionality, and subsequent introduction of
the azide moiety. Removal of the isopropylidene protec-
tive group in SAA 1 by acidolysis exposed the cis-diol
(10) van Well, R. M.; Overkleeft, H. S.; Overhand, M.; Vang
Carstenen, E.; van der Marel, G. A.; van Boom, J. H. Tetrahedron Lett.
2000, 41, 9331-9335. (b) van Well, R. M.; Marinelli, L.; Erkelens, K.;
van der Marel, G. A.; Lavecchia, A.; Overkleeft, H. S.; van Boom, J.
H.; Kessler, H.; Overhand, M. Eur. J. Org. Chem. 2003, 2303-2313.
(11) Glycol cleavage could similarly be effected by sodium periodate
although the reaction proceeded sluggishly.
(8) (a) Du, M.; Hindsgaul, O. Synlett 1997, 395-397. (b) Malmberg,
M.; Rehnberg, N. Synlett 1996, 361-362.
(9) (a) Kumar, V. A. Eur. J. Org. Chem. 2002, 2021-2032. (b)
Heasman, J. Dev. Biol. 2002, 243, 209-214. (c) Summerton, J. Biochim.
Biophys. Acta 1999, 1489, 141-158. (d) Summerton, J.; Weller, D.
Antisense Nucleic Acid Drug Dev. 1997, 7, 187-195.
(12) The azide functionality proved to be stable under these reducing
conditions as no deterioration of 2 was observed when subjected to
the same reaction conditions.
(13) Kiliani, H. Ber. Dtsch. Chem. Ges. 1885, 18, 3066-3072.
8332 J. Org. Chem., Vol. 69, No. 24, 2004

Carbohydrate-Derived Morpholine Amino Acids
SCHEME 2a
a Reagents and conditions: (i) 4 M HCl/MeOH (1/4 v/v), 50 °C, 2 h, 59%; (ii) H5IO6, THF, 30 min, 95%; (iii) R-NH2 (1.1 equiv), NaCNBH3
(4.2 equiv), trimethyl orthoformate/MeOH (1/2 v/v), AcOH, 3 Å mol sieves, 16 h, 8a; 22% and 8b; 22%.
1
FIGURE 1. Parts of the H NMR spectra of 8a and 8b (400 MHz, CDCl3).
tion followed directly by reductive amination of the crude
dialdehyde furnished, after silica column chromatogra-
phy, the diastereoisomeric morpholines 8a and 8b, both
in 22%.
in 53%. Finally, oxidation of the primary hydroxyl in 11
was examined. We have previously shown that the
2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO)/[bis(ace-
toxy)iodo]benzene (BAIB)-mediated oxidation is a power-
ful means to chemo- and regioselectively obtain thiogly-
curonic acids.16 Gratifyingly, this mild procedure proved
effective for the transformation of 11 into δ-MAA 12a,
without affecting the nitrogen of the morpholine, in 61%
yield. The C2-epimer of 12a was constructed from 2,5-
anhydromannitol 14, which was obtained from D-(+)-
glucosamine by nitrous deamination and NaBH4 reduc-
tion, as described by Cassel et al.17 Ensuing selective
mesylation of the resulting anhydromannitol 1318 and
nucleophilic substitution with sodium azide furnished 14
in 45% over two steps. Periodic acid-mediated ring-
The 2,6-cis configuration and 2,6-trans configuration
of 8a and 8b, respectively, were established by compari-
1
son of the H spectra (see Figure 1). The large geminal
(2J3ax,3eq ) 11.1 Hz) and vicinal (3J3ax,2 ) 11.1 Hz) coupling
constants confirmed a anti-periplanar relationship be-
tween H3ax and H2 in the case of 8a. For 8b, a large
geminal (2J3ax,3eq ) 11.6 Hz) and moderate vicinal (3J3ax,2
) 4.1 Hz) coupling constant were observed, indicating a
gauche relationship between H3ax and H2.
The unsuccessful attempts to suppress or circumvent
epimerization during the glycol cleavage and ensuing
reductive amination, together with the moderate yield
and laborious separation, prompted us to select a se-
quence of reactions that excludes an intermediate â-keto
ester. To this end, 2,5-anhydroglucitol 9 (Scheme 3) was
prepared following a route described previously by our
laboratory and that involves the acidic dehydration of
D-(+)-mannitol, acetonation of the 1,3-cis-diol system, and
consecutive introduction of the primary azide.15 Acid-
catalyzed methanolysis of the isopropylidene group pro-
duced triol 10, which was subjected to glycol cleavage and
reductive insertion of benzylamine to give morpholine 11
(14) (a) Brittain, D. E. A.; Watterson, M. P.; Claridge, T. D. W.;
Smith, M. D.; Fleet, G. W. J. J. Chem. Soc., Perkin Trans. 1 2000,
3655-3665. (b) Hungerford, N. L.; Claridge, T. D. W.; Watterson, M.
P.; Aplin, R. T.; Moreno, A.; Fleet, G. W. J. J. Chem. Soc., Perkin Trans.
1 2000, 3666-3679. (c) Hungerford, N. L.; Fleet, G. W. J. J. Chem.
Soc., Perkin Trans. 1 2000, 3680-3685. (d) Fairbanks, A. J.; Fleet, G.
W. J. Tetrahedron 1995, 51, 3881-3894.
(15) Timmer, M. S. M.; Verdoes, M.; Sliedregt, L. A. J. M.; van der
Marel, G. A.; van Boom, J. H.; Overkleeft, H. S. J. Org. Chem. 2003,
68, 9406-9411.
(16) (a) van den Bos, L. J.; Code´e, J. D. C.; van der Toorn, J. C.;
Boltje, T. J.; van Boom, J. H.; Overkleeft, H. S.; van der Marel, G. A.
Org. Lett. 2004, 6, 2165-2168. (b) De Mico, A.; Margarita, R.; Parlanti,
L.; Vescovi, A.; Piancatelli, G. J. Org. Chem. 1997, 62, 6974-6977.
J. Org. Chem, Vol. 69, No. 24, 2004 8333

Grotenbreg et al.
SCHEME 3a
a Reagents and conditions: (i) TFA/MeOH (1/3 v/v), 1 h, quant; (ii) H5IO6, THF, 30 min; (iii) benzylamine (1.1 equiv), NaCNBH3 (4.2
equiv), trimethyl orthoformate/MeOH (1/3 v/v), AcOH, 3 Å mol sieves, 16 h, 11; 53% and 15; 52% (two steps); (iv) TEMPO (0.2 equiv),
BAIB (2 equiv), DCM, 0 °C, 6 h, 12a; 61% and 12b; 68%; (v) MsCl (1.0 equiv), pyridine, -40 °C, 1 h to 0 °C, 16 h; (vi) NaN3 (2.5 equiv),
DMF, 70 °C, 48 h, 45% (two steps).
SCHEME 4a
a Reagents and conditions: (i) 1 M NaOH/THF (1/2 v/v), 3 h, then Amberlite IR-120 (H+), 98%; (ii) repetitive deprotection piperidine/
NMP (1/4 v/v); condensation: Fmoc-aa-OH (3 equiv) or N3-Xaa-OH (2 equiv), BOP (3 equiv), HOBt (3 equiv), DiPEA (3.5 equiv), NMP;
(iii) PMe3 (16 equiv), 1,4-dioxane/H2O (10/1 v/v); (iv) TFA/DCM (1/99 v/v), 4 × 10 min; (v) PyBOP (5 equiv), HOBt (5 equiv), DiPEA (15
equiv), DMF, 16 h, 19; 71% and 21; 63%; (vi) NaIO4 (2 equiv), THF/DMF/H2O (3/1/1 v/v/v), 16 h; (vii) benzylamine (1.5 equiv), NaCNBH3
(5 equiv), trimethylorthoformate/MeOH (1/2 v/v), AcOH, 16 h, 63% (two steps); (viii) TFA/DCM (1/1 v/v), 30 min, 77%.
opening and reductive amination gave morpholine 15
(52%) that was subjected to TEMPO/BAIB oxidation to
provide δ-MAA 12b in 68%.
At this stage, the application of MAAs as peptidomi-
metic compounds was explored and ꢀ-MAA 5a was
selected for incorporation in GS. Nonapeptide 18a (Scheme
4) was assembled on 4-(4-hydroxymethyl-3-methoxyphen-
oxy)butyric acid (HMPB) functionalized 4-methylbenzhy-
drylamine (MBHA) resin 17 using standard Fmoc-based
SPPS protocols. The terminal azide in 18a was subjected
(17) Cassel, S.; Debaig, C.; Benvegnu, T.; Chaimbault, P.; Lafosse,
M.; Plusquellec, D.; Rollin, P. Eur. J. Org. Chem. 2001, 875-896.
(18) Guthrie, R. D.; Jenkins, I. D.; Watters, J. J.; Wright, M. W.;
Yamasaki, R. Aust. J. Chem. 1982, 35, 2169-2173.
8334 J. Org. Chem., Vol. 69, No. 24, 2004

Carbohydrate-Derived Morpholine Amino Acids
B (MeCN), and C (0.5% aq TFA) and coupled to a mass
instrument with a custom-made electronspray interface (ESI)
was used. For reversed-phase HPLC purification of the pep-
tides, an automated HPLC system supplied with a semiprep-
erative C18 column (10.0 mm i.d. × 250 mm, 5 µm particle size)
was used. The applied buffers were A (H2O), B (MeCN), and
C (1.0% aq TFA).
to Staudinger reduction, and the peptide was released
from the solid support by mild acidolysis and subse-
quently cyclized under highly dilute conditions to give
fully protected 19 in 71% (route A).6 Liberation of the
Boc protective groups, followed by HPLC purification,
produced peptide 20 in 77%, which was characterized by
1H NMR to reveal that the peptide prevalently adopts a
â-sheet secondary structure reminiscent of the native
peptide.19 Encouraged by these results, we decided to
examine whether MAA-containing peptidic constructs are
also accessible through the glycol cleavage/reductive
amination strategy when applied to SAAs that are
already embedded in oligopeptide sequences. Thus, sa-
ponification of 2 gave SAA 16 in 98%. Following the
sequence of reactions as described above for compound
19, resin-anchored nonapeptide 18b was constructed
through SPPS, from which GS analogue 21 was readily
prepared in 63%.20 Treatment of the cis-diol-containing
peptide with NaIO4 and reductive amination furnished
19 in 63% (route B), which was deprotected to produce
20. The MAA-containing GS analogue 20 obtained from
both routes were spectroscopically and spectrometrically
identical.
In conclusion, ꢀ-morpholine amino acids, bearing sev-
eral different substituents on the nitrogen of the mor-
pholine core structure, were synthesized from furanoid
ꢀ-SAAs via a two-step oxidative glycol cleavage/reductive
amination approach. Diastereoisomeric mixtures of
δ-MAAs were obtained when the corresponding furanoid
δ-SAAs were subjected to the same sequence of events.
To prevent epimerization during oxidative ring opening,
an alternative scheme was developed, through which 2,5-
anhydroglucitol and 2,5-anhydromannitol were readily
transformed into their diastereoisomerically pure δ-MAA
counterparts. We further demonstrated that ꢀ-MAA-
containing GS analogue 19 could be obtained in two ways;
by directly employing 5a as building block or by first
preparing GS analogue 21, featuring ꢀ-SAA 16, which is
subsequently subjected to our ring-opening/ring-closing
approach.
Methyl 3,6-Anhydro-7-azido-2,7-dideoxy-D-allo-hepto-
nate (2). To a mixture of methyl ester 1 (5.03 g, 18.56 mmol)
in MeOH (75 mL) was added 2 M aq HCl (25 mL), and the
solution was stirred overnight. After being neutralized with 1
M aq NaOH (50 mL), the mixture was partially concentrated
and extracted with EtOAc (3×). The combined organic layers
were dried (MgSO4), filtered, and concentrated. Silica gel
column chromatography (50% f 100% EtOAc in light PE)
yielded the title compound as a clear oil (3.52 g, 15.25 mmol,
82%). 1H NMR (400 MHz, CDCl3): δ ) 4.15 (ddd, 1H, H3, J3,2a
) J3,2b ) 6.5 Hz, J3,4 ) 6.3 Hz), 4.06 (dd, 1H, H5, J5,6 ) 5.4 Hz,
J5,4) 6.3 Hz), 4.00 (dd, 1H, H6, J6,7 ) 4.3 Hz, J6,5 ) 5.4 Hz),
3.95 (dd, 1H, H4, J4,5 ) J4,3 ) 6.3 Hz), 3.57 (dd, 1H, H7a, J7a,6
) 3.4 Hz, J7a,7b ) 13.3 Hz), 3.31 (dd, 1H, H7b, J7b,6 ) 4.3 Hz,
J7b,7a ) 13.3 Hz), 2.77 (dd, 1H, H2a, J2a,3 ) 6.5 Hz, J2a,2b ) 16.3
Hz), 2.69 (dd, 1H, H2b, J2b,3 ) 6.5 Hz, J2b,2a ) 16.3 Hz). 13C
NMR (100 MHz, CDCl3): δ ) 172.3 (C1), 82.8 (C6), 79.1 (C3),
74.6 (C4), 72.1 (C5), 52.1 (C7), 52.0 (OMe), 37.9 (C2). ATR-IR
(thin film) 3396.4, 2956.2, 2098.4, 1728.1, 1438.8, 1400.2,
1274.9, 1172.6, 1097.4, 1037.6, 987.5, 910.3, 850.5, 829.3, 731.0
cm-1. [R]23D ) +80.4 (c ) 1.0, CH2Cl2). MS (ESI): m/z ) 232.1
[M + H]+, 253.8 [M + Na]+, 463.0 [2M + H]+.
Methyl 3,7-Anhydro-5-aza-8-azido-5-benzyl-2,4,5,6,8-
pentadeoxy-D-glycero-D-allo-octonate (4a). Clear oil (668
mg, 2.2 mmol, 54%). 1H NMR (400 MHz, CDCl3): δ ) 7.29
(m, 5H, Har), 4.07 (m, 1H, H3), 3.82 (m, 1H, H7), 3.67 (s, 3H,
OMe), 3.54 (d, 1H, CH2 Bn, JCHa,CHb ) 13.1 Hz), 3.47 (d, 1H,
CH2 Bn, JCHb,CHa ) 13.1 Hz), 3.24 (dd, 1H, H8a, J8a,7 ) 6.6 Hz,
J8a,8b ) 12.9 Hz), 3.10 (dd, 1H, H8b, J8b,7 ) 3.9 Hz, J8b,8a ) 12.9
Hz), 2.81 (ddd, 1H, H4eq, J4eq,6eq ) J4eq,3 ) 1.9 Hz, J4eq,4ax
)
10.9 Hz), 2.67 (ddd, 1H, H6eq, J6eq,4eq ) J6eq,7 ) 2.0 Hz, J6eq,6ax
) 10.9 Hz), 2.53 (dd, 1H, H2a, J2a,3 ) 7.7 Hz, J2a,2b ) 15.3 Hz),
2.38 (dd, 1H, H2b, J2b,3 ) 5.3 Hz, J2a,2b ) 15.3 Hz), 1.88 (dd,
1H, H6ax, J6ax,6eq ) J6ax,7 ) 10.7 Hz), 1.87 (dd, 1H, H4ax, J4ax,4eq
) J4ax,3 10.7 Hz). 13C NMR (100 MHz, CDCl3): δ ) 171.0 (C1),
137.3 (Cq Bn), 129.0 128.3 128.1 127.2 (CHar), 75.2 (C7), 72.5
(C3), 62.8 (CH2 Bn), 57.2 (C4), 54.6 (C6), 52.7 (C8), 51.7 (OMe),
38.6 (C2). ATR-IR (thin film) 2094.6, 1735.8, 1454.2, 1436.9,
1348.1, 1330.8, 1288.4, 1251.7, 1213.1, 1168.8, 1149.5, 1110.9,
1056.9, 1028.0, 999.1, 956.6, 920.0, 742.5, 700.1 cm-1. [R]23
D
) -7.4 (c ) 1.0, CH2Cl2). MS (ESI): m/z ) 305.0 [M + H]+,
Experimental Section
327.1 [M + Na]+.
General Methods. Reactions were monitored by TLC
analysis using DC-fertigfolien (Schleicher & Schuell, F1500,
LS254) with detection by spraying with 20% H2SO4 in EtOH,
(NH4)6Mo7O24‚4H2O (25 g/L), and (NH4)4Ce(SO4)4‚2H2O (10
g/L) in 10% sulfuric acid or by spraying with a solution of
ninhydrin (3 g/L) in EtOH/AcOH (20/1 v/v), followed by
charring at ∼150 °C. Column chromatography was performed
on Fluka silica gel (0.04-0.063 mm) and size-exclusion chro-
matography on Sephadex LH-20. For LC/MS analysis, an
HPLC system (detection simultaneously at 214 and 254 nm)
equipped with an analytical C18 column (4.6 mm i.d. × 250
mm, 5 µm particle size) in combination with buffers A (H2O),
Methyl 3,7-Anhydro-5-aza-8-azido-5-p-methoxybenzyl-
2,4,5,6,8-pentadeoxy-D-glycero-D-allo-octonate (4b). Clear
1
oil (358 mg, 1.12 mmol, 36%). H NMR (400 MHz, CDCl3): δ
) 7.21 (d, 2H, Har, J ) 8.6 Hz), 6.85 (d, 2H, Har, J ) 8.6 Hz),
4.06 (m, 1H, H3), 3.79 (m, 4H, H7, Me PMB), 3.67 (s, 3H, OMe),
3.50 (d, 1H, CH2 PMB, JCHa,CHb ) 12.8 Hz), 3.40 (d, 1H, CH2
PMB, JCHb,CHa ) 12.8 Hz), 3.25 (dd, 1H, H8a, J8a,7 ) 6.8 Hz,
J8a,8b ) 12.8 Hz), 3.10 (dd, 1H, H8b, J8b,7 ) 3.8 Hz, J8b,8a ) 12.8
Hz), 2.80 (ddd, 1H, H4eq, J4eq,6eq ) J4eq,3 ) 1.8 Hz, J4eq,4ax
)
11.1 Hz), 2.66 (ddd, 1H, H6eq, J6eq,4eq ) J6eq,7 ) 1.8 Hz, J6eq,6ax
) 11.1 Hz), 2.53 (dd, 1H, H2a, J2a,3 ) 7.8 Hz, J2a,2b ) 15.4 Hz),
2.39 (dd, 1H, H2b, J2b,3 ) 5.3 Hz, J2a,2b ) 15.4 Hz), 1.85 (dd,
1H, H6ax, J6ax,6eq ) J6ax,7 ) 10.8 Hz), 1.84 (dd, 1H, H4ax, J4ax,4eq
) J4ax,3 ) 10.8 Hz). 13C NMR (100 MHz, CDCl3): δ ) 171.0
(C1), 158.7 (Cq PMB), 130.1 (CHar), 129.2 (Cq PMB), 113.6
(CHar), 75.1 (C7), 72.5 (C3), 62.1 (CH2 PMB), 57.1 (C4), 55.1
(Me PMB), 54.5 (C6), 52.7 (C8), 51.7 (OMe), 38.6 (C2). ATR-
IR (thin film) 2094.6, 1735.8, 1510.2, 1436.9, 1346.2, 1244.0,
1170.7, 1109.0, 1056.9, 1033.8, 817.8 cm-1. [R]23D ) -5.0 (c )
1.0, CHCl3). MS (ESI): m/z ) 355.2 [M + H]+, 357.0 [M +
Na]+.
(19) Upon perusal of the acquired data reported in the Experimental
Section, it was found that the coupling constants (3JNH,HR) and chemical
shift perturbation (∆δHR) for the proteinogenic residues in peptide 20
follow a similar trend compared to native GS. These distinctive features
validate a â-sheet conformation in GS analogues, as we have previously
observed: Grotenbreg, G. M.; Kronemeijer, M.; Timmer, M. S. M.; El
Oualid, F.; van Well, R. M.; Verdoes, M.; Spalburg, E.; van Hooft, P.
A. V.; de Neeling, A. J.; Noort, D.; van Boom, J. H.; van der Marel, G.
A.; Overkleeft H. S.; Overhand, M. J. Org. Chem., in press.
(20) To facilitate the characterization of GS analogue 21, a small
aliquot was deprotected and purified by reversed-phase HPLC to
produce the unprotected peptide in 69% yield.
Methyl 3,7-Anhydro-5-aza-8-azido-5-benzhydryl-2,4,5,
6,8-pentadeoxy-D-glycero-D-allo-octonate (4c). Clear oil
J. Org. Chem, Vol. 69, No. 24, 2004 8335

Grotenbreg et al.
(95 mg, 0.25 mmol, 38%). 1H NMR (400 MHz, CDCl3): δ )
7.27 (m, 10H, Har), 4.22 (s, 1H, HCPh2), 4.13 (m, 1H, H3), 3.87
(m, 1H, H7), 3.63 (s, 3H, OMe), 3.16 (dd, 1H, H8a, J8a,7 ) 6.8
742.5, 700.1 cm-1. [R]23 ) -13.6 (c ) 1.0, CHCl3). MS (ESI):
D
m/z ) 419.2 [M + H]+, 441.2 [M + Na]+. HRMS: calcd for
C21H30N4O5H 419.22890, found 419.22794.
Hz, J8a,8b ) 13.0 Hz), 3.01 (dd, 1H, H8b, J8b,7 ) 3.5 Hz, J8b,8a
)
Methyl 3,7-Anhydro-5-aza-8-azido-5-allyl-2,4,5,6,8-pen-
13.0 Hz), 2.79 (ddd, 1H, H4eq, J4eq,6eq ) J4eq,3 ) 2.0 Hz, J4eq,4ax
) 11.3 Hz), 2.66 (ddd, 1H, H6eq, J6eq,4eq ) J6eq,7 ) 2.0 Hz, J6eq,6ax
) 11.3 Hz), 2.46 (dd, 1H, H2a, J2a,3 ) 8.4 Hz, J2a,2b ) 15.1 Hz),
2.30 (dd, 1H, H2b, J2b,3 ) 4.8 Hz, J2a,2b ) 15.1 Hz), 1.79 (dd,
tadeoxy-D-glycero-D-allo-octonate (4g). Clear oil (121 mg,
1
0.48 mmol, 41%). H NMR (400 MHz, CDCl3): δ ) 5.82 (m,
1H, CH All), 5.19 (m, 2H, CH2 All), 4.05 (m, 1H, H3), 3.82 (m,
1H, H7), 3.69 (s, 3H, OMe), 3.23 (dd, 1H, H8a, J8a,7 ) 6.6 Hz,
J8a,8b ) 13.0 Hz), 3.11 (dd, 1H, H8b, J7,8b ) 4.1 Hz, J8b,8a ) 13.0
Hz), 3.00 (m, 2H, CH2 All), 2.86 (ddd, 1H, H4eq, J4eq,6eq ) J4eq,3
) 1.9 Hz, J4eq,4ax ) 11.2 Hz), 2.75 (ddd, 1H, H6eq, J6eq,4eq ) J6eq,7
) 1.9 Hz, J6eq,6ax ) 11.2 Hz), 2.56 (dd, 1H, H2a, J2a,3 ) 7.7 Hz,
J2a,2b ) 15.4 Hz), 2.43 (dd, 1H, H2b, J2b,3 ) 5.8 Hz, J2b,2a ) 15.4
Hz), 1.85 (dd, 1H, H6ax, J6ax,6eq ) J6ax,7 ) 10.9 Hz), 1.81 (dd,
1H, H4ax, J4ax,4eq ) J4ax,3 ) 10.8 Hz). 13C NMR (100 MHz,
CDCl3): δ ) 171.0 (C1), 134.2 (CH All), 118.6 (CH2 All), 75.1
(C7), 72.5 (C3), 61.7 (CH2 All), 57.2 (C4), 54.7 (C6), 52.8 (C8),
51.8 (OMe), 38.7 (C2). ATR-IR (thin film) 2098.4, 1735.8,
1434.9, 1342.4, 1288.4, 1172.6, 1110.9, 1064.6, 995.2, 925.8
cm-1. [R]23D ) -12.8 (c ) 1.0, CH2Cl2). MS (ESI): m/z ) 255.0
[M + H]+. HRMS: calcd for C11H18N4O3H 255.14517, found
255.14462.
1H, H6ax, J6ax,6eq ) J6ax,7 ) 11.1 Hz), 1.74 (dd, 1H, H4ax, J4ax,3
)
10.5 Hz, J4ax,4eq ) 11.1 Hz). 13C NMR (100 MHz, CDCl3): δ )
171.0 (C1), 141.7 (Cq Ph), 128.6, 127.8, 127.1 (CHar), 76.0 (CH
Ph2), 75.4 (C7), 72.7 (C3), 55.9 (C4), 53.5 (C6), 52.7 (C8), 51.7
(OMe), 38.6 (C2). ATR-IR (thin film) 2094.6, 1735.8, 1490.9,
1450.4, 1436.9, 1282.6, 1251.7, 1168.8, 1110.9, 1055.0, 1028.0,
763.8, 746.4, 705.9 cm-1. [R]23 ) -2.4 (c ) 1.0, CHCl3). MS
D
(ESI): m/z ) 381.1 [M + H]+, 403.1 [M + Na]+.
Methyl 3,7-Anhydro-5-aza-8-azido-5-(tert-butylglyci-
nyl)-2,4,5,6,8-pentadeoxy-D-glycero-D-allo-octonate (4d).
Clear oil (87 mg, 0.266 mmol, 59%). 1H NMR (400 MHz,
CDCl3): δ ) 4.11 (m, 1H, H3), 3.87 (m, 1H, H7), 3.69 (s, 3H,
OMe), 3.28 (dd, 1H, H8a, J7,8a ) 6.5 Hz, J8a,8b ) 12.9 Hz), 3.17
(dd, 1H, H8b, J7,8b ) 4.1 Hz, J8a,8b ) 12.9 Hz), 3.14 (m, 2H, HR
Gly), 2.88 (ddd, 1H, H4eq, J4eq,6eq ) J4eq,3 ) 1.7 Hz, J4eq,4ax
)
Methyl 3,7-Anhydro-5-aza-8-azido-5-isopropyl-2,4,5,6,8-
10.9 Hz), 2.80 (ddd, 1H, H6eq, J6eq,7 ) J6eq,4eq ) 1.7 Hz, J6eq,6ax
) 10.9 Hz), 2.56 (dd, 1H, H2a, J2a,3 ) 7.5 Hz, J2a,2b ) 15.3 Hz),
pentadeoxy-D-glycero-D-allo-octonate (4h). Clear oil (110
1
mg, 0.43 mmol, 33%). H NMR (400 MHz, CDCl3): δ ) 3.98
2.43 (dd, 1H, H2b, J2b, ) 5.6 Hz, J2a,2b ) 15.3 Hz), 2.15 (dd,
3
(m, 1H, H3), 3.75 (m, 1H, H7), 3.63 (s, 3H, OMe), 3.23 (dd, 1H,
1H, H6ax, J6ax,6eq ) J6ax,7 ) 10.9 Hz), 2.12 (dd, 1H, H4ax, J4ax,4eq
) J4ax,3 ) 10.9 Hz), 1.47 (s, 9H, t-Bu). 13C NMR (100 MHz,
CDCl3): δ ) 170.8, 169.1 (C1, CdO t-Bu), 81.3 (Cq t-Bu), 75.0
(C7), 72.4 (C3), 59.5 (CR Gly), 56.5 (C4) 54.1 (C6), 52.6 (C8), 51.7
(OMe), 38.5 (C2), 28.0 (CH3 t-Bu). ATR-IR (thin film) 2098.4,
H8a, J8a,7 ) 6.4 Hz, J8a, 8b ) 12.9 Hz), 3.11 (dd, 1H, H8b, J7,8b
4.2 Hz, J8a,8b ) 12.9 Hz), 2.75 (ddd, 1H, H4eq, J4eq,6eq ) J4eq,3
)
)
1.9 Hz, J4eq,4ax ) 11.1 Hz), 2.63 (m, 2H, H6eq, CH i-Pr), 2.51
(dd, 1H, H2a, J2a,3 ) 7.4 Hz, J2a,2b ) 15.3 Hz), 2.37 (dd, 1H,
H2b, J2b,3 ) 5.7 Hz, J2b,2a ) 15.3 Hz), 1.99 (dd, 1H, H6ax, J6ax,6eq
) J6ax,7 ) 10.7 Hz), 1.95 (dd, 1H, H4ax, J4ax,4eq ) J4ax,3 ) 10.7
Hz), 0.99 (s, 3H, CH3 i-Pr), 0.97 (s, 3H, CH3 i-Pr). 13C NMR
(100 MHz, CDCl3): δ ) 171.0 (C1), 75.2 (C7), 73.9 (C3), 54.5
(CH i-Pr), 52.9 (C4, C8), 51.8 (OMe), 50.4 (C6), 38.7 (C2), 18.1
(CH3 i-Pr), 18.0 (CH3 i-Pr). ATR-IR (thin film) 2098.4, 1737.7,
1735.8, 1442.7, 1365.5, 1218.9, 1149.5, 1064.6 cm-1. [R]23
)
D
-4.4 (c ) 1.0, CH2Cl2). HRMS: calcd for C14H24N4O5H
329.18195, found 329.18140.
Methyl 3,7-Anhydro-5-aza-8-azido-5-(tert-butyl-L-alani-
nyl)-2,4,5,6,8-pentadeoxy-D-glycero-D-allo-octonate (4e).
Clear oil (110 mg, 0.43 mmol, 33%). 1H NMR (400 MHz,
CDCl3): δ ) 4.01 (m, 1H, H3), 3.81 (m, 1H, H7), 3.69 (s, 3H,
OMe), 3.29 (dd, 1H, H8a, J7,8a ) 6.6 Hz, J8a,8b ) 12.9 Hz), 3.19
(q, 1H, HR Ala, JR,â ) 7.1 Hz), 3.14 (dd, 1H, H8b, J7,8b ) 4.2 Hz,
J8a,8b ) 12.9 Hz), 2.85 (ddd, 1H, H4eq, J4eq,6eq ) J4eq,3 ) 2.0 Hz,
J4eq,4ax ) 10.9 Hz), 2.73 (ddd, 1H, H6eq, J6eq,7 ) J6eq,4eq ) 1.9
Hz, J6eq,6ax ) 10.9 Hz), 2.56 (dd, 1H, H2a, J2a,3 ) 7.6 Hz, J2a,2b
) 15.4 Hz), 2.42 (dd, 1H, H2b, J2b, 3 ) 5.6 Hz, J2a,2b ) 15.4 Hz),
2.33 (dd, 1H, H6ax, J6ax,6eq ) J6ax,7 ) 10.7 Hz), 2.21 (dd, 1H,
1436.9, 1350.1, 1257.5, 1168.8, 1109.0, 1060.8, 999.1 cm-1
.
[R]23 ) -14.6 (c ) 1.0, CH2Cl2). MS (ESI): m/z 257.2 [M +
D
H]+, 279.0 [M + Na]+.
3,7-Anhydro-5-aza-8-azido-5-benzyl-2,4,5,6,8-penta-
deoxy-D-glycero-D-allo-octonic Acid (5a). Clear oil (102 mg,
0.35 mmol, quant). 1H NMR (400 MHz, MeOD): δ ) 7.22 (m,
5H, Har), 3.93 (m, 1H, H3), 3.67 (m, 1H, H7), 3.45 (d, 1H, CH2
Bn, JCHa,CHb ) 12.8 Hz), 3.39 (d, 1H, CH2 Bn, JCHb,CHa ) 12.8
Hz), 3.13 (m, 2H, H8), 2.84 (ddd, 1H, H4eq, J4eq,6eq ) J4eq,3 ) 2.0
H4ax, J4ax,4eq ) J4ax,3 ) 10.7 Hz), 1.47 (s, 9H, t-Bu), 1.26 (d, 3H,
Hz, J4eq,4ax ) 11.3 Hz), 2.62 (ddd, 1H, H6eq, J6eq,4eq ) J6eq,7
)
Hâ Ala, JR,â ) 7.1 Hz). 13C NMR (100 MHz, CDCl3): δ ) 171.9,
171.0 (C1, CdO t-Bu), 81.1 (Cq t-Bu), 75.3 (C7), 72.9 (C3), 62.7
(CR Ala), 52.7 (C6, C8), 51.7 (OMe), 51.6 (C4), 38.5 (C2), 28.0
(CH3 t-Bu), 14.5 (Câ Ala). ATR-IR (thin film): 2098.4, 1722.3,
1436.9, 1367.4, 1350.1, 1255.6, 1318.0, 1145.6, 1114.8, 1091.6,
1062.7, 1049.2, 993.3, 952.8, 881.4, 846.7 cm-1. [R]23D ) -23.2
(c ) 1.0, CH2Cl2). MS (ESI): m/z ) 343.1 [M + H]+, 365.2 [M
+ Na]+.
2.0 Hz, J6eq,6ax ) 11.1 Hz), 2.35 (dd, 1H, H2a, J2a,3 ) 6.3 Hz,
J2a,2b ) 14.4 Hz), 2.13 (dd, 1H, H2b, J2b,3 ) 7.3 Hz, J2a,2b ) 14.4
Hz), 1.79 (dd, 1H, H6ax, J6ax,6eq ) J6ax,7 ) 11.0 Hz), 1.74 (dd,
1H, H4ax, J4ax,3 ) 10.3 Hz, J4ax,4eq ) 11.3 Hz). 13C NMR (100
MHz, MeOD): δ ) 177.4 (C1), 136.8 (Cq Bn), 129.0, 127.8, 126.9
(CHar), 74.4 (C7), 73.7 (C3), 62.6 (CH2 Bn), 57.5 (C4), 54.5 (C6),
52.6 (C8), 42.2 (C2). ATR-IR (thin film): 3033.8, 2786.9, 2933.5,
2380.0, 2100.3, 1569.9, 1494.7, 1398.3, 1361.7, 1296.1, 1191.9,
1107.1, 1051.1, 1028.0, 925.8, 742.5, 698.2 cm-1. [R]23D ) +16.0
(c ) 1.0, MeOH). MS (ESI): m/z ) 290.8 [M + H]+, 313.0 [M
+ Na]+.
Methyl 3,7-Anhydro-5-aza-8-azido-5-(tert-butyl-L-phen-
ylalaninyl)-2,4,5,6,8-pentadeoxy-D-glycero-D-allo-octonate
(4f). Clear oil (103 mg, 0.25 mmol, 45%). 1H NMR (400 MHz,
CDCl3): δ ) 7.23 (m, 5H, CHar), 3.98 (m, 1H, H3), 3.76 (m,
1H, H7), 3.70 (s, 3H, OMe), 3.33 (dd, 1H, HR, JR,âb ) 6.6 Hz,
JR,âa ) 9.1 Hz), 3.27 (dd, 1H, H8a, J8a,7 ) 6.8 Hz, J8a,8b ) 13.0
Hz), 3.10 (dd, 1H, H8b, J8b,7 ) 4.1 Hz, J8b,8a ) 13.0 Hz), 3.00
3,7-Anhydro-5-aza-8-azido-5-p-methoxybenzyl-2,4,5,6,8-
pentadeoxy-D-glycero-D-allo-octonic Acid (5b). Clear oil
(117 g, 0.37 mmol, 94%). 1H NMR (400 MHz, MeOD): δ ) 7.14
(d, 2H, Har, J ) 8.5 Hz), 6.76 (d, 2H, Har, J ) 8.5 Hz), 3.92 (m,
1H, H3), 3.67 (m, 1H, H7), 3.64 (s, 3H, OMe), 3.48 (m, 2H, CH2
PMB), 3.15 (m, 2H, H8), 2.86 (ddd, 1H, H4eq, J4eq,3 ) 1.5 Hz,
J4eq,6eq ) 2.0 Hz, J4eq,4ax ) 11.4 Hz), 2.69 (ddd, 1H, H6eq, J6eq,4eq
(m, 2H, H4eq, Hâa), 2.89 (dd, 1H, Hâb, Jâb,R ) 6.6 Hz, Jâb,âa
)
13.4 Hz), 2.69 (ddd, 1H, H6eq, J6eq,4eq ) J6eq,7 ) 2.0 Hz, J6eq,6ax
) 11.1 Hz), 2.57 (dd, 1H, H2a, J2a,3 ) 7.7 Hz, J2a,2b ) 15.4 Hz),
2.45 (dd, 1H, H2b, J2b,3 ) 5.5 Hz, J2b,2a ) 15.4 Hz), 2.40 (dd,
1H, H6ax, J6ax,6eq ) J6ax,7 ) 10.7 Hz), 1.81 (dd, 1H, H4ax, J4ax,4eq
) J4ax,3 ) 10.8 Hz), 1.35 (s, 9H, CH3 t-Bu). 13C NMR (100 MHz,
CDCl3): δ ) 171.0, 170.2 (C1, CdO t-Bu), 137.8 (Cq Ph), 129.6,
129.4, 129.2, 128.2, 126.3 (CHar), 81.4 (CHq t-Bu), 75.4 (C7),
72.9 (C3), 69.6 (CHR), 53.9 (C6), 52.5 (C8), 51.7 (OMe), 51.2 (C4),
38.4 (C2), 35.3 (Câ), 28.1 (CH3 t-Bu). ATR-IR (thin film): 2098.4,
1422.3, 1367.4, 1288.4, 1253.6, 1145.6, 1112.9, 1064.6, 844.8,
) J6eq,7 ) 2.0 Hz, J6eq,6ax ) 11.4 Hz), 2.33 (dd, 1H, H2a, J2a,3
)
7.0 Hz, J2a,2b ) 15.0 Hz), 2.21 (dd, 1H, H2b, J2b,3 ) 6.3 Hz, J2a,2b
) 15.0 Hz), 1.93 (dd, 1H, H6ax, J6ax,6eq ) J6ax,7 ) 11.4 Hz), 1.87
(dd, 1H, H4ax, J4ax,4eq ) J4ax,3 ) 11.4 Hz). 13C NMR (100 MHz,
MeOD): δ ) 176.3 (C1), 160.9 (Cq PMB), 132.2 (CHar), 128.5
(Cq PMB), 114.9 (CHar), 75.7 (C7), 74.0 (C3), 63.0 (CH2 PMB),
57.8 (C4), 55.7 (Me PMB), 55.2 (C6), 53.9 (C8), 41.4 (C2). ATR-
IR (thin film) 2098.4, 1705.0, 1612.4, 1512.1, 1404.1, 1242.1,
8336 J. Org. Chem., Vol. 69, No. 24, 2004

Carbohydrate-Derived Morpholine Amino Acids
1180.4, 1110.9, 1033.8, 817.8, 732.9 cm-1. [R]23D ) +20.0 (c )
1.0, CHCl3). MS (ESI): m/z ) 321.1 [M + H]+, 343.0 [M +
Na]+. HRMS: calcd for C15H20N4O4H 321.15573, found
321.15512.
(CHar), 81.6 (CHq t-Bu), 75.2 (C7), 72.6 (C3), 69.5 (CHR), 53.6
(C6), 52.6 (C8), 51.1 (C4), 38.5 (C2), 35.3 (Câ), 28.0 (CH3 t-Bu).
ATR-IR (thin film) 2098.4, 1720.4, 1450.4, 1365.5, 1257.5,
1149.5, 840.9 cm-1. [R]23 ) -8.8 (c ) 1.0, CH2Cl2). HRMS:
D
calcd for C20H29N4O5H 405.21325, found 405.21136.
3,7-Anhydro-5-aza-8-azido-5-benzhydryl-2,4,5,6,8-pen-
tadeoxy-D-glycero-D-allo-octonic Acid (5c). White solid
(109 mg, 0.30 mmol, quant). 1H NMR (400 MHz, MeOD): δ )
7.17 (m, 10H, Har), 4.08 (s, 1H, HCPh2), 3.95 (m, 1H, H3), 3.64
3,7-Anhydro-5-aza-8-azido-5-allyl-2,4,5,6,8-pentadeoxy-
D-glycero-D-allo-octonic Acid (5g). White solid (45 mg, 0.19
mmol, 78%). 1H NMR (400 MHz, MeOD): δ) 5.81 (m, 1H, CH
All), 5.24 (m, 2H, CH2 All), 4.01 (m, 1H, H3), 3.77 (m, 1H, H7),
(m, 1H, H7), 2.92 (m, 2H, H8), 2.72 (ddd, 1H, H4eq, J4eq,6eq
J4eq,3 ) 1.9 Hz, J4eq,4ax ) 11.2 Hz), 2.54 (ddd, 1H, H6eq, J6eq,4eq
) J6eq,7 ) 1.9 Hz, J6eq,6ax ) 11.0 Hz), 2.23 (dd, 1H, H2a, J2a,3
)
3.22 (m, 2H, H8), 3.18 (m, 2H, CH2 All), 3.05 (ddd, 1H, H4eq
,
)
J4eq,6eq ) J4eq,3 ) 1.7 Hz, J4eq,4ax ) 11.6 Hz), 2.91 (ddd, 1H, H6eq
,
7.2 Hz, J2a,2b ) 15.2 Hz), 2.04 (dd, 1H, H2b, J2b,3 ) 5.8 Hz, J2a,2b
) 15.2 Hz), 1.61 (dd, 1H, H6ax, J6ax,6eq ) J6ax,7 ) 11.0 Hz), 1.56
(dd, 1H, H4ax, J4ax,3 ) 10.5 Hz, J4ax,4eq ) 11.2 Hz). 13C NMR
(100 MHz, MeOD): δ ) 177.5 (C1), 143.5 (Cq Ph), 129.6, 129.0,
128.1 (CHar), 77.6 (CH Ph2), 76.2 (C7), 74.8 (C3), 57.7 (C4), 55.1
(C6), 54.0 (C8), 42.0 (C2). ATR-IR (thin film) 2098.4, 1712.7,
1581.5, 1450.4, 1265.2, 1110.9, 1056.9, 933.5, 732.9, 702.0
cm-1. [R]23D ) +23.8 (c ) 1.0, CHCl3). MS (ESI): m/z ) 367.2
[M + H]+, 389.3 [M + Na]+. HRMS: calcd for C20H22N4O3H
367.17647, found 367.17575.
J6eq,4eq ) J6eq,7 ) 1.7 Hz, J6eq,6ax ) 11.6 Hz), 2.41 (dd, 1H, H2a,
J2a,3 ) 7.0 Hz, J2a,2b ) 15.5 Hz), 2.34 (dd, 1H, H2b, J2b,3 ) 6.1
Hz, J2b,2a ) 15.5 Hz), 2.10 (dd, 1H, H6ax, J6ax,6eq ) J6ax,7 ) 11.2
Hz), 2.03 (dd, 1H, H4ax, J4ax,4eq ) J4ax,3 ) 11.1 Hz). 13C NMR
(100 MHz, MeOD): δ ) 175.5 (C1), 132.6 (CH All), 121.9 (CH2
All), 75.4 (C7), 73.4 (C3), 61.9 (CH2 All), 57.2 (C4), 54.7 (C6),
53.7 (C8), 40.5 (C2). ATR-IR (thin film) 2094.6, 1705.0, 1573.8,
1423.4, 1296.1, 1188.1, 1110.91051.1, 999.1, 927.7, 819.7 cm-1
.
[R]23D ) +12.0 (c ) 1.0, MeOH). HRMS: calcd for C10H16N4O3H
241.12952, found 241.12821.
3,7-Anhydro-5-aza-8-azido-5-(tert-butylglycinyl)-2,4,5,6,8-
pentadeoxy-D-glycero-D-allo-octonic Acid (5d). Clear oil
3,7-Anhydro-5-aza-8-azido-5-isopropyl-2,4,5,6,8-penta-
deoxy-D-glycero-D-allo-octonic Acid (5h). White solid (53
mg, 0.22 mmol, quant). 1H NMR (400 MHz, MeOD): δ ) 4.04
(m, 1H, H3), 3.81 (m, 1H, H7), 3.27 (m, 2H, H8), 3.15 (ddd, 1H,
1
(61 mg, 0.19 mmol, quant). H NMR (400 MHz, CDCl3): δ )
4.04 (m, 1H, H3), 3.83 (m, 1H, H7), 3.22 (dd, 1H, H8a, J8,7 ) 6.1
Hz, J8a,8b ) 12.9 Hz), 3.16 (dd, 1H, H8b, J8b,7 ) 4.3 Hz, J8b,8a
)
H
4eq, J4eq,6eq ) J4eq,3 ) 1.7 Hz, J4eq,4ax ) 11.6 Hz), 2.99 (m, 2H,
6eq, CH i-Pr), 2.42 (dd, 1H, H2a, J2a,3 ) 6.3 Hz, J2a,2b ) 15.2
12.9 Hz), 3.15 (d, 1H, HR Gly, JRa,Rb ) 16.7 Hz), 3.09 (d, 1H,
H
HR Gly, JRb,Ra ) 16.7 Hz), 2.90 (ddd, 1H, H4eq, J4eq,6eq ) J4eq,3
)
Hz), 2.36 (dd, 1H, H6ax, J6ax,6eq ) J6ax,7 ) 11.2 Hz), 2.30 (m,
2H, H4ax, H2b), 1.14 (s, 3H, CH3 i-Pr), 1.11 (s, 3H, CH3 i-Pr).
13C NMR (100 MHz, CDCl3): δ ) 176.0 (C1), 75.1 (C7), 73.9
(C3), 58.0 (CH i-Pr), 53.7, 53.5 (C4, C8), 51.0 (C6), 42.2 (C2),
17.8 (CH3 i-Pr). ATR-IR (thin film)) 3375.2, 1211.9, 1733.9,
1635.5, 1575.7, 1398.3, 1107.1, 1020.3 cm-1. [R]23D ) +11.2 (c
) 1.0, MeOH). MS (ESI): m/z ) 243.0 [M + H]+. HRMS: calcd
for C10H18N4O3H 243.14517, found 243.14368.
1.8 Hz, J4eq,4ax ) 11.0 Hz), 2.82 (ddd, 1H, H6eq, J6eq,7 ) J6eq,4eq
) 1.8 Hz, J6eq,6ax ) 11.0 Hz), 2.50 (dd, 1H, H2a, J2a,3 ) 7.1 Hz,
J2a,2b ) 15.5 Hz), 2.36 (dd, 1H, H2b, J2b, ) 6.0 Hz, J2a,2b
)
3
15.5 Hz), 2.17 (dd, 1H, H6ax, J6ax,6eq ) J6ax,7 ) 11.0 Hz), 2.12
(dd, 1H, H4ax, J4ax,3 ) J4ax,4eq ) 11.0 Hz), 1.39 (s, 9H, t-Bu). 13
C
NMR (100 MHz, CDCl3): δ ) 174.4 (C1), 168.7 (CdO t-Bu),
81.7 (Cq t-Bu), 74.5 (C7), 72.0 (C3), 59.0 (CR Ala), 56.0 (C4), 53.7
(C6), 52.6 (C8), 38.7 (C2), 28.0 (CH3 t-Bu). ATR-IR (thin film)
2977.9, 2098.4, 1728.1, 1367.4, 1288.4, 1222.8, 1149.5, 1110.9,
1058.8, 914.2, 842.8, 731.0 cm-1. [R]23D ) +7.8 (c ) 1.0, CHCl3).
MS (ESI): m/z ) 315.0 [M + H]+, 337.3 [M + Na]+. HRMS:
calcd for C13H23N4O5H 315.16630, found 315.15637.
Methyl 2,5-Anhydro-6-azido-6-deoxy-D-allonate (7). Cy-
clohexylidene-protected 6 (1.45 g, 4.88 mmol) was dissolved
in MeOH (20 mL) and treated with 4 M aq HCl (5 mL). The
solution was stirred 2 h at 50 °C and poured into saturated
aqueous NaHCO3. The aqueous layer was extracted with
EtOAc (3×), and the combined organic layers were dried
(MgSO4) and concentrated. Purification by silica column
chromatography (50% f 100% EtOAc in light PE) gave diol 7
3,7-Anhydro-5-aza-8-azido-5-(tert-butyl-L-alaninyl)-
2,4,5,6,8-pentadeoxy-D-glycero-D-allo-octonic Acid (5e).
White solid (57 mg, 0.17 mmol, 78%). 1H NMR (400 MHz,
MeOD): δ ) 3.86 (m, 1H, H3), 3.67 (m, 1H, H7), 3.17 (d, 2H,
H8, J8,7 ) 5.0 Hz), 3.19 (q, 1H, HR Ala, JR,â ) 7.1 Hz), 2.84
(ddd, 1H, H4eq, J4eq,6eq ) J4eq,3 ) 2.0 Hz, J4eq,4ax ) 11.3 Hz),
2.68 (ddd, 1H, H6eq, J6eq,7 ) J6eq,4eq ) 2.0 Hz, J6eq,6ax ) 11.0
Hz), 2.36 (dd, 1H, H2a, J2a,3 ) 6.8 Hz, J2a,2b ) 15.1 Hz), 2.24
1
as a clear oil (628 mg, 2.88 mmol, 59%). H NMR (200 MHz,
CDCl3): δ ) 4.44 (d, 1H, H2, J2,3 ) 4.4 Hz), 4.43 (dd, 1H, H3,
J3,4 ) J3,2) 4.4 Hz), 4.09 (m, 2H, H4, H5), 3.80 (s, 3H, OMe),
3.60 (dd, 1H, H6a, J6a,5 ) 3.3 Hz, J6a,6b ) 13.5 Hz), 3.45 (dd,
1H, H7b, J7b,6 ) 4.7 Hz, J7b,7a ) 13.5 Hz). 13C NMR (50 MHz,
CDCl3): δ ) 171.3 (C1), 82.4, 81.9 (C2, C5), 74.0, 72.2 (C4, C5),
52.6 (OMe), 52.1 (C6). MS (ESI): m/z ) 218.1 [M + H]+, 239.9
[M + Na]+.
(dd, 1H, H2b, J2b, ) 6.6 Hz, J2a,2b ) 15.1 Hz), 2.21 (dd, 1H,
3
H6ax, J6ax,6eq ) J6ax,7 ) 10.9 Hz), 2.04 (dd, 1H, H4ax, J4ax,3 )
10.3 Hz, J4ax,4eq ) 11.3 Hz), 1.41 (s, 9H, t-Bu), 1.26 (d, 3H, Hâ
Ala, Jâ,R ) 7.1 Hz). 13C NMR (100 MHz, MeOD): δ ) 175.2
(C1), 172.1 (CdO t-Bu), 80.9 (Cq t-Bu), 74.8 (C7), 73.4 (C3), 62.9
(CR Ala), 52.5, 52.2, 52.1 (C4, C6, C8), 40.1 (C2), 26.9 (CH3 t-Bu),
13.4 (Câ Ala). ATR-IR (thin film): 2098.4, 1722.3, 1581.5,
1367.4, 1255.6, 1218.9, 1145.6, 1089.7, 1031.8, 991.3, 846.7
Methyl 2,6-Anhydro-4-aza-7-azido-4-benzyl-3,4,5,7-tet-
radeoxy-D-glycero-D-ribo-heptonate (8a). Diol 7 (109 mg,
0.47 mmol) was treated as described in the general procedure
for glycol cleavage and reductive amination (Supporting
Information). Silica gel column chromatography of the result-
ing mixture (10% EtOAc in light PE) first gave 8b (32 mg,
0.11 mmol, 22%). Upon further elution of the column (10% f
15% EtOAc in light PE), the lower running title compound 8a
(31 mg, 0.11 mmol, 22%) was obtained as a clear oil. 1H NMR
(400 MHz, CDCl3): δ ) 7.31 (m, 5H, Har), 4.30 (dd, 1H, H2,
J2,3eq ) 2.7 Hz, J2,3ax ) 10.9 Hz), 3.80 (m, 1H, H6), 3.58 (d, 1H,
cm-1. [R]23 ) -3.6 (c ) 1.0, MeOH). MS (ESI): m/z ) 243.0
D
[M + H]+.
3,7-Anhydro-5-aza-8-azido-5-(tert-butyl-L-phenylalani-
nyl)-2,4,5,6,8-pentadeoxy-D-glycero-D-allo-octonic Acid
(5f). White solid (55 mg, 0.14 mmol, 45%). 1H NMR (400 MHz,
CDCl3): δ ) 7.20 (m, 5H, CHar), 4.00 (m, 1H, H3), 3.79 (m,
1H, H7), 3.38 (dd, 1H, HR, JR,âb ) 6.1 Hz, JR,âa ) 9.4 Hz), 3.28
(dd, 1H, H8a, J8a,7 ) 6.3 Hz, J8a,8b ) 12.9 Hz), 3.15 (dd, 1H,
H8b, J8b,7 ) 4.3 Hz, J8b,8a ) 12.9 Hz), 3.01 (m, 2H, H4eq, Hâa),
2.91 (dd, 1H, Hâb, Jâb,R ) 6.1 Hz, Jâb,âa ) 13.3 Hz), 2.75 (ddd,
1H, H6eq, J6eq,4eq ) J6eq,7 ) 1.8 Hz, J6eq,6ax ) 11.1 Hz), 2.60 (dd,
1H, H2a, J2a,3 ) 7.7 Hz, J2a,2b ) 15.7 Hz), 2.50 (dd, 1H, H2b,
CH2 Bn, JCHa,CHb ) 12.9 Hz), 3.52 (d, 1H, CH2 Bn, JCHb,CHa
)
12.9 Hz), 3.42 (dd, 1H, H7a, J7a,6 ) 6.3 Hz, J7a,7b ) 12.9 Hz),
3.29 (dd, 1H, H7b, J7b,6 ) 4.8 Hz, J7b,7a ) 12.9 Hz), 3.08 (ddd,
1H, H3eq, J3eq,5eq ) 1.7 Hz, J3eq,2 ) 2.7 Hz, J3eq,3ax ) 11.0 Hz),
2.74 (ddd, 1H, H5eq, J5eq,3eq ) J5eq,6 ) 1.7 Hz, J5eq,5ax ) 11.1
Hz), 2.14 (dd, 1H, H3ax, J3ax,3eq ) J3ax,2 ) 11.0 Hz), 1.97 (dd,
1H, H5ax, J5ax,5eq ) J5ax,6 ) 11.1 Hz). 13C NMR (100 MHz,
CDCl3): δ ) 169.6 (C1), 136.9 (Cq Bn), 129.0, 128.4, 127.8, 127.4
(CHar), 75.1 (C2), 74.9 (C6), 62.8 (CH2 Bn), 54.5 (C5), 54.2 (C3),
52.7 (C7), 52.2 (OMe). ATR-IR (thin film) 2098.4, 1759.0,
J2b,3 ) 5.7 Hz, J2b,2a ) 15.7 Hz), 2.41 (dd, 1H, H6ax, J6ax,6eq
)
J6ax,7 ) 10.9 Hz), 2.33 (dd, 1H, H4ax, J4ax,4eq ) J4ax,3 ) 10.9 Hz),
1.34 (s, 9H, CH3 t-Bu). 13C NMR (100 MHz, CDCl3): δ ) 175.6
(C1), 170.2 (CdO t-Bu), 137.6 (Cq Ph), 129.3, 128.2, 126.4
J. Org. Chem, Vol. 69, No. 24, 2004 8337

Grotenbreg et al.
1288.4, 1203.5, 1118.6, 1064.6, 740.6, 702.0 cm-1. [R]23D ) -7.6
(c ) 1.0, CH2Cl2). HRMS: calcd for C14H18N4O3H 291.14517,
found 291.14508.
1053.1, 999.1, 862.1, 754.1, 698.2 cm-1. [R]D ) +4.8 (c ) 1.0,
MeOH). HRMS: calcd for C13H17N4O3H 277.12952, found
277.12817.
Methyl 2,6-Anhydro-4-aza-7-azido-4-benzyl-3,4,5,7-tet-
2,6-Anhydro-4-aza-7-azido-4-benzyl-3,4,5,7-tetradeoxy-
D-glycero-D-arabino-heptonic Acid (12b). Compound 15 (95
mg, 0.36 mmol) was treated following the same procedure as
for 11, to deliver MAA 12b (68 mg, 0.24 mmol, 68%) as a clear
radeoxy-D-glycero-D-arabino-heptonate (8b). Clear oil (32
1
mg, 0.11 mmol, 22%). H NMR (400 MHz, CDCl3): δ ) 7.31
(m, 5H, Har), 4.42 (dd, 1H, H2, J2,3eq ) 2.2 Hz, J2,3ax ) 4.1 Hz),
4.33 (m, 1H, H6), 3.52 (d, 1H, CH2 Bn, JCHa,CHb ) 13.3 Hz),
3.46 (d, 1H, CH2 Bn, JCHb,CHa ) 13.3 Hz), 3.37 (dd, 1H, H7a,
J7a,6 ) 4.5 Hz, J7a,7b ) 13.0 Hz), 3.29 (dd, 1H, H7b, J7b,6 ) 5.8
Hz, J7b,7a ) 13.0 Hz), 3.10 (ddd, 1H, H3eq, J3eq,5eq ) J3eq,2 ) 2.2
Hz, J3eq,3ax ) 11.6 Hz), 2.74 (ddd, 1H, H5eq, J5eq,6 ) 1.7 Hz,
1
oil. H NMR (400 MHz, MeOD): δ ) 7.36 (m, 5H, Har), 4.30
(1H, H2, J2,3eq ) 3.2 Hz, J2,3ax ) 4.1 Hz), 4.24 (m, 1H, H6), 3.69
(d, 1H, CH2 Bn, JCHa,CHb ) 13.1 Hz), 3.65 (d, 1H, CH2 Bn,
JCHb,CHa ) 13.1 Hz), 3.37 (dd, 1H, H7a, J7a,6 ) 4.7 Hz, J7a,7b
)
13.0 Hz), 3.30 (dd, 1H, H7b, J7b,6 ) 5.5 Hz, J7b,7a ) 13.0 Hz),
3.16 (ddd, 1H, H3eq, J3eq,5eq ) 1.7 Hz, J3eq,2 ) 3.2 Hz, J3eq,3ax
11.8 Hz), 2.75 (ddd, 1H, H5eq, J5eq,3eq ) 1.7 Hz, J5eq,6 ) 2.6 Hz,
J5eq,5ax ) 11.6 Hz), 2.61 (dd, 1H, H3ax, J3ax,2 ) 4.3 Hz, J3ax,3eq
J5eq,3eq ) 2.2 Hz, J5eq,5ax ) 11.2 Hz), 2.41 (dd, 1H, H3ax, J3ax,2
)
)
4.1 Hz, J3ax,eq ) 11.6 Hz), 1.97 (dd, 1H, H5ax, J5ax,6 ) 9.9 Hz,
J5ax,5eq ) 11.2 Hz). 13C NMR (100 MHz, CDCl3): δ ) 171.3 (C1),
137.2 (Cq Bn), 128.7, 128.2, 127.3 (CHar), 72.6 (C2), 70.9 (C6),
62.6 (CH2 Bn), 54.9 (C5), 53.5 (C3), 52.7 (C7), 51.9 (OMe). ATR-
IR (thin film) 2098.4, 1743.5, 1272.9, 1203.5, 1126.4, 1026.1,
)
11.8 Hz), 2.35 (dd, 1H, H5ax, J5ax,6 ) 9.3 Hz, J5ax,5eq ) 11.6 Hz).
13C NMR (100 MHz, MeOD): δ ) 175.7 (C1) 136.2 (Cq Bn),
130.8, 129.6, 129.1 (CHar), 73.7, (C2), 71.6 (C6), 63.3 (CH2 Bn),
55.2 (C5), 54.5 (C3), 53.4 (C7). ATR-IR (thin film) 2098.4,
1716.5, 1602.7, 1456.2, 1396.4, 1274.9, 1213.1, 1120.6, 752.2,
700.1 cm-1. [R]23D ) +12.8 (c ) 0.1, MeOH). MS (ESI): m/z )
277.0 [M + H]+, 298.9 [M + Na]+. HRMS: calcd for C13H17N4-
O3H 277.12952, found 277.12799.
740.6, 702.0 cm-1. [R]23 ) +49.6 (c ) 1.0, CH2Cl2). HRMS:
D
calcd for C14H18N4O3H 291.14517, found 291.14456.
2,5-Anhydro-6-azido-6-deoxy-D-glucitol (10). Azide 9 (98
mg, 0.43 mmol) was dissolved in MeOH (3 mL), and TFA (1
mL) was added. The mixture was stirred for 1 h, and all
solvents were removed in vacuo. Residual traces of acid were
removed by repeated coevaporation with toluene to furnish the
title compound 10 (83 mg, 0.43 mmol) quantitatively as a clear
oil. 1H NMR (400 MHz, MeOD): δ ) 3.96 (m, 2H, H2, H3), 3.80
(dd, 1H, H4, J4,3 ) 1.9 Hz, J4,5 ) 3.6 Hz), 3.71 (m, 2H, H5, H1a),
3.64 (dd, 1H, H1b, J1b,2 ) 5.7 Hz, J1b,1a ) 11.7 Hz), 3.36 (dd,
1H, H6a, J6a,5 ) 6.5 Hz, J6a,6b ) 12.8 Hz), 3.32 (dd, 1H, H6b,
J6b,5 ) 5.1 Hz, J6b,6a ) 12.8 Hz). 13C NMR (100 MHz, MeOD):
δ ) 85.2 (C5), 82.9 (C2), 80.7 (C4), 78.8 (C3), 61.8 (C1), 53.8 (C6).
ATR-IR (thin film) 3357.4, 3103.3, 2924.5, 2104.2, 1635.5,
1338.5, 1280.6, 1045.3, 974.0, 923.8 cm-1. [R]23D ) +49.0 (c )
1.0, MeOH). MS (ESI): m/z ) 190.0 [M + H]+, 212.0 [M +
Na]+.
2,5-Anhydro-6-azido-6-deoxy-D-mannitol (14). Anhydro-
mannitol 13 (6.65 g, 20 mmol) was mesylated as described by
Guthrie et al.18 The mesylate (2.20 g, 9.1 mmol) was subse-
quently dissolved in DMF (50 mL), NaN3 (1.47 g, 22.7 mmol,
2.5 equiv) was added, and the mixture was stirred at 70 °C
for 48 h. Evaporation of the volatiles and silica column
chromatography (0% f 10% of MeOH in EtOAc) produced 14
(1.73 g, 9.1 mmol, 45% over two steps) as a clear oil. 1H NMR
(400 MHz, MeOD): δ) 3.94 (dd, 1H, H3, J3,2 ) J3,4 ) 6.1 Hz),
3.89 (dd, 1H, H4, J4,3 ) J4,5 ) 6.1 Hz), 3.84 (m, 1H, H5), 3.76
(m, 1H, H2), 3.65 (dd, 1H, H1a, J1a,2 ) 3.4 Hz, J1a,1b ) 11.9 Hz),
3.55 (dd, 1H, H1b, J1b,2 ) 4.9 Hz, J1b,1a ) 11.9 Hz), 3.42 (dd,
1H, H6a, J6a,5 ) 3.6 Hz, J6a,6b ) 13.1 Hz), 3.28 (dd, 1H, H6b,
J6b,5 ) 5.6 Hz, J6b,6a ) 13.1 Hz). 13C NMR (100 MHz, MeOD):
δ ) 84.9 (C2), 83.4 (C5), 79.2 (C4), 78.2 (C3), 63.0 (C1), 53.3 (C6).
ATR-IR (thin film) 3357.8, 2923.9, 2104.2, 1645.2, 1440.7,
2,6-Anhydro-4-aza-7-azido-4-benzyl-3,4,5,7-tetradeoxy-
D-glycero-D-ribo-heptitol (11). Triol 10 (693 mg, 3.5 mmol)
was subjected to glycol cleavage and reductive amination, as
described in the general procedure (Supporting Information),
1280.6, 1109.0, 1045.3, 933.5 cm-1. [R]23 ) +73.4 (c ) 1.0,
D
MeOH). MS (ESI): m/z ) 190.0 [M + H]+, 212.1 [M + Na]+.
1
to deliver 11 (486 mg, 1.85 mmol, 53%) as a white solid. H
NMR (400 MHz, CDCl3): δ ) 7.30 (m, 5H, Har), 3.87 (m, 1H,
2,6-Anhydro-4-aza-7-azido-4-benzyl-3,4,5,7-tetradeoxy-
D-glycero-D-arabino-heptitol (15). Triol 14 (280 mg, 1.4
mmol) was subjected to glycol cleavage and reductive amina-
tion, as described in the general procedure (Supporting
Information), to obtain title compound 15 (191 mg, 0.73 mmol,
H6), 3.76 (m, 1H, H2), 3.65 (dd, 1H, H1a, J1a,2 ) 3.6 Hz, J1a,1b
)
11.6 Hz), 3.55 (dd, 1H, H1b, J1b,2 ) 6.3 Hz, J1b,1a ) 11.6 Hz),
3.53 (s, 2H, CH2 Bn), 3.28 (dd, 1H, H7a, J7a,6 ) 6.3 Hz, J7a,7b
)
12.9 Hz), 3.22 (dd, 1H, H7b, J7b,6 ) 4.1 Hz, J7b,7a ) 12.9 Hz),
2.72 (ddd, 2H, H3eq, H5eq, J3eq,5eq ) J3eq,2 ) J5eq,3eq ) J5eq,6 ) 1.7
1
52%) as a clear oil. H NMR (400 MHz, CDCl3): δ ) 7.30 (m,
Hz, J3eq,3ax ) J5eq,5ax ) 10.6 Hz), 1.98 (dd, 1H, H3ax, J3ax,3eq
)
5H, Har), 4.16 (m, 1H, H6), 3.92 (m, 1H, H2), 3.84 (dd, 1H, H1a,
J3ax,2 ) 11.0 Hz), 1.95 (dd, 1H, H5ax, J5ax,5eq ) J5ax,6 11.0 Hz).
13C NMR (100 MHz, CDCl3): δ ) 130.7 (Cq Bn), 129.2, 128.4,
127.4 (CHar), 76.3 (C2), 75.2 (C6), 64.0 (C1), 63.1 (CH2 Bn), 55.0
(C5), 53.8 (C3), 53.0 (C7). ATR-IR (thin film) 3386.8, 2923.9,
J1a,2 ) 5.8 Hz, J1a,1b ) 11.6 Hz), 3.74 (dd, 1H, H1b, J1b,2 ) 3.4
Hz, J1b,1a ) 11.6 Hz), 3.61 (dd, 1H, H7a, J7a,6 ) 7.3 Hz, J7a,7b
)
12.9 Hz), 3.47 (s, 2H, CH2 Bn), 3.27 (dd, 1H, H7b, J7b,6 ) 4.8
Hz, J7b,7a ) 12.9 Hz), 2.58 (dd, 1H, H3a, J3a,2 ) 3.4 Hz, J3a,3b
)
2877.6, 2098.4, 1450.4, 1288.4, 1118.6, 1064.6, 918.1 cm-1
.
11.4 Hz), 2.53 (dd, 1H, H5a, J5a,6 ) 3.4 Hz, J5a,5b ) 11.6 Hz),
2.47 (dd, 1H, H3b, J3b,2 ) 5.6 Hz, J3b,3a ) 11.4 Hz), 2.32 (dd,
1H, H5b, J5b,6 ) 6.1 Hz, J5b,5a ) 11.6 Hz). 13C NMR (100 MHz,
CDCl3): δ ) 137.1 (Cq Bn), 128.9, 128.5, 127.4 (CHar), 71.3,
71.2 (C2, C6), 64.8 (C1), 63.1 (CH2 Bn), 54.4 (C3), 54.2 (C5), 51.8
(C7). IR (thin film) 3384.5, 2936.2, 2094.6, 1454.2, 1265.2,
1149.6, 1112.9, 1053.1, 912.3, 742.5, 698.2 cm-1. [R]23D ) +3.8
(c ) 1.0, CH2Cl2). HRMS: calcd for C13H18N4O2H 263.15025,
found 263.15015.
[R]23D ) +2.0 (c ) 1.0, CH2Cl2). HRMS: calcd for C13H18N4O2H
263.15025, found 263.14951.
2,6-Anhydro-4-aza-7-azido-4-benzyl-3,4,5,7-tetradeoxy-
D-glycero-D-ribo-heptonic Acid (12a). To a vigorously stirred
solution of morpholine 11 (79 mg, 0.30 mmol) in DCM (1 mL)
and water (0.5 mL), that was cooled to 0 °C, were added
TEMPO (9.4 mg, 0.06 mmol, 0.2 equiv) and BAIB (193 mg,
0.6 mmol, 2 equiv). After 6 h, the reaction was quenched with
MeOH and the mixture was evaporated to dryness. Silica gel
column chromatography (0% f 10% of a mixture of n-BuOH/
AcOH/water (1/1/1 v/v/v) in EtOAc) provided 12a as a clear
oil (50 mg, 0.18 mmol, 61%). 1H NMR (400 MHz, MeOD): δ )
7.38 (m, 5H, Har), 4.24 (m, 1H, H2), 3.96 (m, 2H, CH2 Bn), 3.87
3,6-Anhydro-7-azido-2,7-dideoxy-D-allo-heptonic Acid
(16). To a solution of ester 2 (350 mg, 1.52 mmol) in THF (4
mL) was added 1 M aq NaOH (2 mL). The mixture was
neutralized after 3 h with Amberlite IR-120 (H+), filtered, and
concentrated. Purification by silica column chromatography
(0% f 2% AcOH in EtOAc) furnished 16, as a clear oil (323
(m, 1H, H6), 3.41 (m, 3H, H7, H3eq), 3.06 (d, 1H, H5eq, J5eq,5ax
)
1
11.4 Hz), 2.51 (dd, 1H, H3ax, J3ax,3eq ) J3ax,2 ) 11.4 Hz), 2.43
(dd, 1H, H5ax, J5ax,5eq ) J5ax,6 ) 11.2 Hz). 13C NMR (100 MHz,
MeOD): δ ) 173.1 (C1), 134.3 (Cq Bn), 131.4, 129.8 (CHar), 75.7
(C2), 74.7 (C6), 62.9 (CH2 Bn), 54.7, 54.4 (C3, C5), 53.4 (C7). IR
(thin film) 2100.3, 1608.5, 1456.2, 1373.2, 1274.9, 1120.6,
mg, 1.49 mmol, 98%). H NMR (400 MHz, CD3OD): δ ) 4.16
(ddd, 1H, H3, J3,2a ) 4.9 Hz, J3,4 ) 5.3 Hz, J3,2b ) 8.4 Hz), 3.96
(m, 2H, H5, H6), 3.84 (dd, 1H, H4, J4,3 ) 5.3 Hz, J4,5 ) 5.4 Hz),
3.51 (dd, 1H, H7a, J7a,6 ) 3.1 Hz, J7a,7b ) 13.2 Hz), 3.29 (dd,
1H, H7b, J7b,6 ) 4.4 Hz, J7b,7a ) 13.2 Hz), 2.67 (dd, 1H, H2a,
8338 J. Org. Chem., Vol. 69, No. 24, 2004

Carbohydrate-Derived Morpholine Amino Acids
J2a,3 ) 4.9 Hz, J2a,2b ) 15.7 Hz), 2.50 (dd, 1H, H2b, J2b,3 ) 8.4
Hz, J2b,2a ) 15.7 Hz). 13C NMR (100 MHz, CD3OD): δ ) 174.6
(C1), 83.9 (C6), 81.2 (C3), 75.7 (C4), 73.0 (C5), 53.5 (C7), 39.4
(C2). ATR-IR (thin film): 3434.6, 2927.7, 2100.3, 1706.9,
1406.0, 1272.9, 1180.4, 1097.4, 1033.8, 977.8, 912.3, 827.4,
748.3 cm-1. [R]23D +54.4 (c ) 1.0, MeOH). MS (ESI): m/z 217.9
[M + H]+, 241.0 [M + Na]+, 435.1 [2M + H]+, 457.1 [2M +
Na]+. HRMS: calcd for C7H11N3O5H 218.07715, found
218.07724.
0.97 (m, 3H, Hγd Val7), 0.93 (m, 6H, Hγ Val2), 0.90 (m, 9H, Hδ
Leu4, Hγu Val7), 0.84 (m, 6H, Hδ Leu9). HRMS: calcd for
C60H94N12O10H 1143.72886, found 1143.72632.
cyclo-[SAA-Val-Orn(Boc)-Leu-DPhe-Pro-Val-Orn-
Leu] (21). In a similar scheme described in route A, preloaded
resin 17 (100 µmol) was elongated in a stepwise fashion, with
a final condensation of SAA 16 (44 mg, 0.2 mmol, 2 equiv),
BOP (132 mg, 0.3 mmol, 3 equiv), HOBt (41 mg, 0.3 mmol, 3
equiv), and DiPEA (58 µL, 0.35 mmol, 3.5 equiv) in NMP (3
mL), to ultimately obtain the title peptide 21 (80 mg, 63 µmol,
63%) as an off-white amorphous solid. An aliquot of 21 (14
mg, 11.0 µmol) was then dissolved in DCM (2 mL) and cooled
to 0 °C, and TFA (2 mL) was added slowly. After the mixture
was stirred for 30 min, the volatiles were removed in vacuo
and the crude peptide was analyzed by LC/MS (tR 14.71 min
(linear gradient 10 f 90% B in 20 min; m/z ) 1070.8 [M +
H]+, 536.1 [M + H]2+), purified by RP-HPLC (linear gradient
of 3.0 CV; 40f50% B; tR ) 1.9 CV) and the combined fractions
were lyophilizated to furnish the unprotected peptide (8.1 mg,
7.6 µmol, 69%) as an amorphous white powder. 1H NMR (600
MHz, CD3OH): δ ) 8.90 (d, 1H, NH DPhe5, JNH,HR ) 3.5 Hz),
8.68 (d, 1H, NHR Orn3, JNH,HR ) 8.1 Hz), 8.62 (d, 1H, NH Leu4,
JNH,HR ) 9.4 Hz), 8.61 (d, 1H, NHR Orn8, JNH,HR ) 8.9 Hz), 8.56
(d, 1H, NH Leu9, JNH,HR ) 8.9 Hz), 8.07 (t, 1H, NH SAA1, JNH,7
) 6.1 Hz), 7.86 (bs, 2H, NHδ Orn3,8), 7.74 (d, 1H, NH Val7,
JNH,HR ) 8.6 Hz), 7.55 (d, 1H, NH Val2, JNH,HR ) 8.5 Hz), 7.38-
7.21 (m, 5H, Har), 4.98 (m, 1H, HR Orn3), 4.71 (m, 1H, HR Orn8),
4.65 (m, 1H, HR Leu4), 4.56 (m, 1H, HR Leu9), 4.51 (m, 1H, HR
DPhe5), 4.34 (m, 1H, HR Pro6), 4.24 (m, 1H, HR Val2), 4.06 (m,
1H, HR Val7), 3.95 (m, 2H, H3, H6 SAA1), 3.86 (dd, 1H, H5 SAA1,
J5,4 ) 5.2 Hz, J5,6 ) 3.0 Hz), 3.78 (dd, 1H, H4 SAA1, J4,5 ) 5.2
Hz, J4,3 ) 6.5 Hz), 3.72 (m, 1H, Hδd Pro6), 3.36 (m, 1H, H7d
SAA1), 3.31 (m, 1H, H7u SAA1), 3.07 (dd, 1H, Hâd DPhe5, Jâd,âu
) 12.6 Hz, Jâd,R ) 5.0 Hz), 3.02 (m, 1H, Hδd Orn3), 2.98 (m,
1H, Hδd Orn8), 2.96 (m, 3H, Hδu Orn3, Hδu Orn8, Hâu DPhe5),
2.50 (m, 3H, H2 SAA1, Hδu Pro6), 2.28 (m, 1H, Hâ Val7), 1.99
(m, 3H, Hâd Pro6, Hâd Orn3, Hâ Val2), 1.83 (m, 1H, Hâd Orn8),
1.74 (m, 2H, H γ Orn3), 1.71 (m, 2H, Hâu, γd Pro6), 1.67 (m, 1H,
cyclo-[MAA-Val-Orn(Boc)-Leu-DPhe-Pro-Val-Orn-
Leu] (19). Route A. Fmoc-based solid-phase peptide synthesis
was performed as described previously,6 starting with pre-
loaded resin 17 (100 µmol), with a final coupling of 5a (64 mg,
0.2 mmol, 2 equiv), BOP (132 mg, 0.3 mmol, 3 equiv), HOBt
(41 mg, 0.3 mmol, 3 equiv), and DiPEA (58 µL, 0.35 mmol, 3.5
equiv) in NMP (2 mL), to ultimately furnish the title compound
19 (96 mg, 71 µmol, 71%) as a white amorphous solid.
Route B. Boc-protected GS analogue 21 (50 mg, 40 µmol)
was dissolved in THF (7.5 mL) and DMF (2.5 mL), and a
solution of sodium periodate (17 mg, 80 µmol, 2 equiv) in water
(2.5 mL) was added. Stirring was continued overnight, after
which the milky suspension was concentrated and partitioned
between water and chloroform. The water layer was extracted
with chloroform (2×), and the combined organic layers were
dried (MgSO4), filtered, and concentrated to quantitatively
produce the crude dialdehyde (50 mg, 40 µmol). Subsequently,
the dialdehyde (25 mg, 20 µmol) was dissolved in MeOH (4
mL) and trimethyl orthoformate (2 mL) and NaCNBH3 (7 mg,
100 µmol, 5 equiv) was added. To this mixture was added a
solution of benzylamine (3.2 µL, 30 µmol, 1.5 equiv) in MeOH
(0.5 mL), trimethyl orthoformate (0.2 mL), and DMF (0.2 mL)
that had been acidified to pH ) 5 with AcOH in advance. After
stirring overnight, all solvents were evaporated and the
mixture was applied to a size exclusion column that was eluted
with MeOH, to yield the title compound 19 (17 mg, 12 µmol,
63%) as white amorphous solid.
cyclo-[MAA-Val-Orn-Leu-DPhe-Pro-Val-Orn-Leu] (20).
A mixture of MAA-containing 19 (17 mg, 12 µmol) in DCM (2
mL) was cooled to 0 °C, treated with TFA (2 mL), and stirred
for 30 min. The solvents were evaporated, and the crude
mixture was analyzed by LC/MS (tR 12.74 min (linear gradient
05 f 90% B in 20 min.; m/z ) 1144.0 [M + H]+, 572.7 [M +
H]2+) followed by semipreparative RP-HPLC purification
(linear gradient of 3.0 CV; 35 f 55% B; tR 2.2 CV), to produce
20 (10.6 mg, 9.3 µmol) in 77% after lyophilization of the pooled
H
âu Orn3), 1.66 (m, 2H, Hγ Orn8), 1.64 (m, 3H, Hâ, γ Leu9), 1.59
(m, 1H, Hγu Pro6), 1.56 (m, 2H, Hâd, Leu4), 1.39 (m, 1H, Hâu
γ
Leu4), 0.95 (m, 3H, Hγd Val7), 0.94 (m, 3H, Hγd Val2), 0.92 (m,
3H, Hγu Val2), 0.90 (m, 6H, Hδ Leu4), 0.88 (m, 3H, Hγu Val7),
0.86 (m, 6H, Hδ Leu9). ATR-IR (thin film): 3278.1, 3071.9,
2959.2, 2935.6, 2873.4, 1669.8, 1636.5, 1539.2, 1464.7, 1456.7,
1437.0, 1203.7, 1182.7, 1135.0, 1033.3, 1020.8, 837.1, 800.1,
722.6, 702.5 cm-1. HRMS: calcd for C53H87N11O12H 1079.6608,
found 1070.6521.
1
fractions. H NMR (600 MHz, CD3OH): δ ) 8.86 (d, 1H, NH
DPhe5, JNH,HR ) 3.8 Hz), 8.65 (d, 1H, NHR Orn8, JNH,HR ) 8.2
Hz), 8.56 (d, 1H, NHR Orn3, JNH,HR ) 8.9 Hz), 8.48 (d, 1H, NH
Leu4, JNH,HR ) 8.7 Hz), 8.21 (d, 1H, NH Leu9, JNH,HR ) 8.4 Hz),
7.89 (d, 1H, NH Val7, JNH,HR ) 7.1 Hz), 7.83 (t, 1H, NH MAA1,
JNH,8 ) 5.8 Hz), 7.47-7.45 (m, 5H, Har), 7.39 (d, 1H, NH Val2,
JNH,HR ) 8.3 Hz), 7.31-7.23 (m, 5H, Har), 4.98 (m, 1H, HR Orn3),
4.63 (m, 1H, HR Leu4), 4.53 (m, 1H, HR DPhe5), 4.43 (m, 2H,
HR Leu9, HR Orn8), 4.35 (m, 2H, HR Pro6, HR Val2), 4.23 (m,
2H, CH2 Bn), 4.11 (m, 1H, H3 MAA1), 3.93 (m, 1H, H7 MAA1),
3.88 (m, 1H, HR Val7), 3.71 (m, 1H, Hδd Pro6), 3.36 (m, 1H, H8d
MAA1), 3.32 (m, 2H, H4d, H6d MAA1), 3.07 (m, 2H, Hâd DPhe5,
H8u MAA1), 2.98 (m, 5H, Hδ Orn3, Hδ Orn8, Hâu DPhe5), 2.75
(m, 1H, H4u MAA1), 2.67 (m, 1H, H6u MAA1), 2.53 (m, 2H, H2d
MAA1, Hδu Pro6), 2.30 (m, 1H, Hâ Val7), 1.95 (m, 3H, Hâ Val2,
Acknowledgment. This work was financially sup-
ported by the Council for Chemical Sciences of The
Netherlands Organization for Scientific Research (CW-
NWO), The Netherlands Technology Foundation (STW),
and DSM Research. Kees Erkelens and Fons Lefeber
are gratefully acknowledged for assistance with NMR
experiments. We thank Nico Meeuwenoord and Hans
van den Elst for their technical assistance.
Supporting Information Available: General experimen-
tal methods and copies of 1H and 13C NMR spectra as well as
2D NMR spectra of compounds 4a, 8a,b, 12a,b, 20, and 21.
This material is available free of charge via the Internet at
http://pubs.acs.org.
Hâd Pro6, Hâd Orn8), 1.88 (m, 1H, Hâd Orn3), 1.75 (m, 5H, Hâu,γ
Orn3, Hγ Orn8), 1.72 (m, 2H, Hâu,γd Pro6), 1.67 (m, 1H, Hâu
Orn3), 1.66 (m, 1H, Hâu Orn8), 1.65 (m, 1H, Hγu Pro6), 1.64 (m,
3H, Hâ,γ Leu9), 1.56 (m, 2H, Hâd, γ Leu4), 1.41 (m, 1H, Hâu Leu4),
JO048630X
J. Org. Chem, Vol. 69, No. 24, 2004 8339