Toward a Total Synthesis of the Immunosuppressant Sanglifehrin A. Preparation of Two Relay Compounds by Degradation and Their Use in the Reassembly of the Natural Product

Article abstract of DOI:10.1021/jo9912395

A potential relay route for the synthesis of the novel immunosuppressive agent sanglifehrin A (1) has been developed. Degradation of 1 by a sequence involving regioselective dihydroxylation of the C26,C27 double bond, followed by periodate cleavage of the resulting diol 4, afforded lactol 2 and macrocyclic aldehyde 3. Intramolecular ketal formation between the 1,3-diol and ketone functions present in 3 gave ketal-aldehyde 5. Lactol 2 was converted into sulfone 14 in four steps. The fragments 5 and 14 were reassembled, using the Julia-Kocienski olefination procedure, to afford intermediate 15, which was converted back to sanglifehrin A (1) after two deprotection steps.

Full text of DOI:10.1021/jo9912395

9632
J . Org. Chem. 1999, 64, 9632-9639
Tow a r d a Tota l Syn th esis of th e Im m u n osu p p r essa n t Sa n glifeh r in
A. P r ep a r a tion of Tw o Rela y Com p ou n d s by Degr a d a tion a n d
Th eir Use in th e Rea ssem bly of th e Na tu r a l P r od u ct
Rainer Metternich,* Donatienne Denni, Binh Thai, and Richard Sedrani*
Preclinical Research, Novartis Pharma AG, CH-4002, Basel, Switzerland
Received August 5, 1999
A potential relay route for the synthesis of the novel immunosuppressive agent sanglifehrin A (1)
has been developed. Degradation of 1 by a sequence involving regioselective dihydroxylation of the
C26,C27 double bond, followed by periodate cleavage of the resulting diol 4, afforded lactol 2 and
macrocyclic aldehyde 3. Intramolecular ketal formation between the 1,3-diol and ketone functions
present in 3 gave ketal-aldehyde 5. Lactol 2 was converted into sulfone 14 in four steps. The
fragments 5 and 14 were reassembled, using the J ulia-Kocienski olefination procedure, to afford
intermediate 15, which was converted back to sanglifehrin A (1) after two deprotection steps.
The discovery of the immunosuppressive natural prod-
uct cyclosporin A (CsA) revolutionized organ transplanta-
tion by dramatically increasing the survival of transplant
recipients.1 Since the introduction of this drug into
clinical practice, the search for novel immunosuppres-
sants has been pursued by many companies, resulting
most notably in the discovery of the macrolides FK5062
and rapamycin3 as clinically useful drugs for the preven-
tion of graft rejection. The macrocyclic undecapeptide
CsA, like FK506 and rapamycin, is a so-called “dual-
domain” inhibitor.4 In the first step it binds to its
intracellular binding protein, cyclophilin (CyP).5 The CyP/
CsA complex then associates with and inhibits the serine/
threonine phosphatase calcineurin.6 It is the formation
of this ternary complex which is ultimately responsible
for the inhibition of T-cell activation by CsA. Since the
time when CyP was identified as a binding protein for
CsA, various research groups have been searching for
novel immunosuppressive CyP ligands. Screening of
microbial fermentation extracts in a cyclophilin binding
assay recently led to the discovery of a novel macrolide,
sanglifehrin A (1), by researchers at Novartis.7 This
macrolide binds to cyclophilin with a 20-fold higher
affinity than CsA.7a,c Moreover, 1 exhibits immunosup-
pressive activity.7a,c The activity profile in vitro is clearly
distinct from that of other immunosuppressive drugs.
These data indicate that 1 represents a novel type of
immunosuppressive agent.
The structure of 1 is quite interesting. The compound
consists of a 22-membered macrocycle, bearing in position
23 a nine-carbon chain terminated by a spirobicyclic
moiety. The macrocyclic part of the molecule contains a
tripeptide subunit consisting of valine and two rather
unusual amino acids, piperazic acid and metatyrosine.
Interestingly, the â-nitrogen of piperazic acid is involved
in amide bond formation. This stands in contrast to other
natural products containing this particular amino acid,
in which usually the R-nitrogen is linked to a carbonyl.8
One of the most remarkable features of the molecule, in
structural terms, is certainly the highly substituted
spirobicyclic oxaazaspiro[5.5]undecanone system (C33-
N42). To the best of our knowledge, no other natural
product described until now contains this substructure.
The spirobicycle contains seven stereocenters, six of
which are contiguous (C33-C38).
* To whom correspondence should be addressed: (R.S.) phone, (+)
41 61 324 2609; fax, (+) 41 61 324 6735; e-mail, richard.sedrani@pharma.
novartis.com. (R.M.) phone, (+) 41 61 696 6260; fax, (+) 41 61 696
6283, e-mail, rainer.metternich@pharma.novartis.com.
(1) Borel, J . F.; Baumann, G.; Chapman, I.; Donatsch, P.; Fahr, A.;
Mueller, E. A.; Vigouret, J .-M. Adv. Pharmacol. (San Diego) 1996, 35,
115-246.
The immunosuppressive activity profile and the struc-
tural attractiveness of sanglifehrin A (1) led us to
(2) Spencer, C. M.; Goa, K. L.; Gillis, J . C. Drugs 1997, 54, 925-
(8) Examples of macrocyclic natural products containing piperazic
acid: (Antibiotic GE3) (a) Sakai, Y.; Yoshida, T.; Tsujita, T.; Ochiai,
K.; Agatsuma, T.; Saitoh, Y.; Tanaka, F.; Akiyama, T.; Akinaga, S.;
Mizukami, T. J . Antibiot. 1997, 50, 659-664. (b) Agatsuma, T.; Sakai,
Y.; Mizukami, T.; Saitoh, Y. J . Antibiot. 1997, 50, 704-708. (Auran-
timycins) (c) Graefe, U.; Schlegel, R.; Ritzau, M.; Ihn, W.; Dornberger,
K.; Stengel, C.; Fleck, W. F.; Gutsche, W.; Haertl, A.; Paulus, E. F. J .
Antibiot. 1995, 48, 119-125. (Verucopeptin) (d) Nishiyama, Y.; Sug-
awara, K.; Tomita, K.; Yamamoto, H.; Kamei, H.; Oki, T. J . Antibiot.
1993, 46, 921-927. (e) Sugawara, K.; Toda, S.; Moriyama, T.; Konishi,
M.; Oki, T. J . Antibiot. 1993, 46, 928-935. (Antibiotic A83586C) (f)
Smitka, T. A.; Deeter, J . B.; Hunt, A. H.; Mertz, F. P.; Ellis, R. M.;
Boeck, L. D.; Yao, R. C. J . Antibiot. 1988, 41, 726-733. (Azinothricin)
(g) Maehr, H.; Liu, C. M.; Palleroni, N. J .; Smallheer, J .; Todaro, L.;
Williams, T. H.; Blount, J . F. J . Antibiot. 1986, 39, 17-25.
975.
(3) Kahan, B. D. Clin. Biochem. 1998, 31, 341-344.
(4) Schreiber, S. L. Science 1991, 251, 283-287.
(5) Handschumacher, R. E.; Harding, M. W.; Rice, J .; Drugge, R.
J .; Speicher, D. W. Science 1984, 226, 544-547.
(6) Liu, J .; Farmer, J . D. J r.; Lane, W. S.; Friedman, J .; Weissman,
I.; Schreiber, S. L. Cell 1991, 66, 807-815.
(7) (a) Sanglier, J .-J .; Quesniaux, V.; Fehr, T.; Hofmann, H.;
Mahnke, M.; Memmert, K.; Schuler, W.; Zenke, G.; Gschwind, L.;
Maurer, C.; Schilling, W. J . Antibiot. 1999, 52, 466-473. (b) Fehr, T.;
Kallen, J .; Oberer, L.; Sanglier, J .-J .; Schilling, W. J . Antibiot. 1999,
52, 474-479. (c) Fehr, T.; Oberer, L.; Quesniaux Ryffel, V.; Sanglier,
J .-J .; Schuler, W.; Sedrani, R. PCT International Patent Application
WO 97/02285-A1, 1997.
10.1021/jo9912395 CCC: $18.00 © 1999 American Chemical Society
Published on Web 12/01/1999

Synthesis of Sanglifehrin A
Sch em e 1
J . Org. Chem., Vol. 64, No. 26, 1999 9633
proximately 10% of two diastereomeric 20,21,26,27-
tetrahydroxysanglifehrins,17 which were easily removed
by column chromatography on silica gel. Interestingly,
when the pseudoenantiomeric (DHQD)2PHAL ligand,
corresponding to AD-mix-â, was used, the reaction was
slower. After the 3 h typically required for complete
conversion using AD-mix-R, significant amounts of start-
ing material were still detected when AD-mix-â was
employed. Longer reaction times resulted in the forma-
tion of large amounts of very polar material, and hence
in lower yields of the isolated 26(R),27(R) diastereomer
of 4. Cleavage of the C26,C27-diol of 4 with sodium
periodate proceeded cleanly to afford the lactol 2 and the
aldehyde 3, each in 87% yield, after chromatographic
separation (Scheme 2). The 1,3-diol and ketone functions
present in 3 were protected by acid-promoted intramo-
lecular ketal formation, affording 5 in 92% yield (Scheme
2). Finally, the phenol in 5 was protected as the TBDMS
ether 6. Thus, an efficient two-step procedure allowed for
the selective degradation of 1. The resulting fragments
2 and 3, or derivatives thereof, are of similar structural
complexity and therefore represent very attractive sub-
targets for a convergent total synthesis of sanglifehrin
A (1). To illustrate this point, we attempted the recon-
struction of 1.
We started investigating the olefination step required
for the formation of the C26,C27 linkage using the
aldehyde 6. Preliminary experiments were conducted
using the 6-phenylhexyl group as a model for the C27-
N42 subunit of sanglifehrin A. Thus, deprotonation of the
phosphonium salt 7 with LDA and reaction of the
resulting phosphorane with aldehyde 6 led to the diene
8 in reasonable yield (eq 1). As could have been expected,
contemplate a total synthesis of the natural product.9,10
We were particularly interested in developing a relay
synthesis of 1,11 in other words a synthesis in which the
natural product is degraded to fragments which can be
reassembled to the original molecule. In this paper, we
report the successful implementation of this strategy,
namely, the degradation of sanglifehrin A (1) into frag-
ments 2 and 3 by oxidative cleavage of the C26,C27
double bond, and the subsequent coupling of derivatives
of 2 and 3, leading to the resynthesis of the natural
product (Scheme 1).
For the oxidative cleavage of one of the exocyclic double
bonds we envisaged a two-step procedure, involving
regioselective dihydroxylation followed by cleavage of the
resulting diol. Initial attempts using the Upjohn osmyl-
ation procedure12 met with little success. Inseparable
mixtures of various polyhydroxylated derivatives of 1
were obtained. We then envisaged using the Sharpless
asymmetric dihydroxylation (AD) reaction. It has indeed
been shown that with this protocol “mono”-dihydroxyla-
tion of polyenes, including conjugated ones, can be
achieved.13,14 We were pleased to find that treatment of
1 under modified AD conditions,15 using (DHQ)2PHAL
as a ligand (AD-mix-R), led to the desired 26(S),27(S)-
dihydroxysanglifehrin A (4) in a remarkable 70% yield
(Scheme 2).16 This product was accompanied by ap-
this nonstabilized Wittig reagent resulted in the prefer-
(13) (a) Xu, D.; Crispino, G. A.; Sharpless, K. B. J . Am. Chem. Soc.
1992, 114, 7570-7571. (b) Becker, H.; Soler, M. A.; Sharpless, K. B.
Tetrahedron 1995, 51, 1345-1376.
(14) For a recent application of the AD reaction to the complex,
polyene-containing natural product rapamycin, see: Sedrani, R.; Thai,
B.; France, J ,; Cottens, S. J . Org. Chem. 1998, 63, 10069-10073.
(15) For a standard procedure, see: Sharpless, K. B.; Amberg, W.;
Bennani, Y. L.; Crispino, G. A.; Hartung, J .; J eong, K.-S.; Kwong, H.-
L.; Morikawa, K.; Wang, Z.-M.; Xu, D.; Zhang, X.-L. J . Org. Chem.
1992, 57, 2768-2771. In this study we added the individual compo-
nents separately instead of using the premixed powder. Instead of
potassium osmate, osmium tetraoxide solution was used. More impor-
tantly, the loads of osmium catalyst and phthalazine ligand were 15-
and 6-fold higher, respectively, than those recommended in the
published standard procedure (see the Experimental Section for more
details).
(9) For a report describing the synthesis of the tripeptide segment
of sanglifehrin A, see: Ba¨nteli, R.; Brun, I.; Hall, P.; Metternich, R.
Tetrahedron Lett. 1999, 40, 2109-2112.
(10) For a synthesis of the sanglifehrin A macrocycle and a total
synthesis of the natural product, see: (a) Nicolaou, K. C.; Ohshima,
T.; Murphy, F.; Barluenga, S.; Xu, J .; Winssinger, N. Chem. Commun.
1999, 809-810. (b) Nicolaou, K. C.; Xu, J .; Murphy, F.; Barluenga, S.;
Baudoin, O.; Wei, H.; Gray, D.; Ohshima, T. Angew. Chem., Int. Ed.
Engl. 1999, 38, 2447-2451.
(16) The absolute configurations of the newly created stereocenters
have not been unambiguously proven. Their assignment is based on
the application of the Sharpless mnemonic device; see: Kolb, H. C.;
Andersson, P. G.; Sharpless, K. B. J . Am. Chem. Soc. 1994, 116, 1278-
1291.
(17) The diastereomers could be separated by HPLC. The regio-
chemical outcome of the tetrahydroxylation was thus determined on
pure samples. No attempt was made to determine the configurations
of the tetrols.
(11) For elegant recent examples of relay syntheses of natural
products, see: (Zaragozic acid A (squalestatin S1)) (a) Stoermer, D.;
Caron, S.; Heathcock, C. H. J . Org. Chem. 1996, 61, 9115-9125. (b)
Stoermer, D.; Mapp, A. K.; Heathcock, C. H. J . Org. Chem. 1996, 61,
9126-9134. (Azadirachtin) (c) Denholm, A. A.; J ennens, L.; Ley, S.
V.; Wood, A. Tetrahedron 1995, 51, 6591-6604.
(12) Van Rheenen, V.; Kelly, R. C.; Cha, D. Y. Tetrahedron Lett.
1976, 1973-1976.

9634 J . Org. Chem., Vol. 64, No. 26, 1999
Metternich et al.
Sch em e 2a
a
Reagents and conditions: (a) 3 mol % OsO4, 6 mol % (DHQ)2PHAL, 3 equiv of K3Fe(CN)6, 3 equiv of K2CO3, 2 equiv of CH3SO2NH2,
1:1 t-BuOH/H2O, rt, 2 h; (b) 2 equiv of NaIO4, 2:1 THF/H2O, rt, 1 h; (c) HF‚pyridine, CH3CN, 0 °C, 1h; (d) 1.2 equiv of MTBSTFA, CH3CN,
50 °C, 1.5 h.
Sch em e 3a
ential formation of the undesired Z C26,C27 olefin.18
While we were considering different approaches for the
formation of the desired E double bond, a publication by
Kocienski, describing a modification of the olefination
procedure developed by Sylvestre J ulia, appeared.19 The
original procedure consists of the one-pot formation of
alkenes by addition of R-lithiated benzothiazol-2-yl sul-
fones to aldehydes.20 This olefination reaction is opera-
a
tionally simpler than the 3-4-step variant reported
earlier by Marc J ulia,21 but suffers from the fact that
stereoselectivities are often low.20b,c Kocienski found that
E/Z selectivities can be influenced by the nature of the
heterocycle on the sulfone. Thus, replacement of the
benzothiazol-2-yl group by a 1-phenyl-1H-tetrazol-5-yl
moiety leads to E alkenes with high selectivities. Though
the examples reported by Kocienski were limited to the
coupling of aliphatic aldehydes and alkyl(1-phenyl-1H-
tetrazol-5-yl) sulfones, we made an attempt using our
substrate 6. We were pleased to find that the reaction of
Reagents and conditions: (a) 3 equiv of NaBH4, MeOH, 0 °C,
2 h; (b) 1.1 equiv of 1-phenyl-1H-tetrazole-5-thiol, 1.1 equiv of
PPh3, 1.1 equiv of DIAD, THF, 0 °C to rt, 30 h; (c) 2.2 equiv of
TESOTf, 2.6 equiv of pyridine, 1:1 Et2O/CH3CN, -50 °C, 0.5 h;
(d) 5 equiv of mCPBA, 10 equiv of NaHCO3, CH2Cl2, rt, 12 h.
metalated 6-phenylhexyl sulfone 9 with 6 resulted in the
highly selective formation of the desired E C26,C27 olefin
10 in an acceptable yield (eq 2). Stimulated by this very
encouraging result, we decided to use this methodology
for the reconstruction of sanglifehrin A (1) from the
fragments 2 and 3.
(18) For an extensive review of the Wittig reaction, see: Maryanoff,
B. E.; Reitz, A. B. Chem. Rev. 1989, 89, 863-927.
(19) Blakemore, P. R.; Cole, W. J .; Kocienski, P. J .; Morley, A. Synlett
1998, 26-28.
It was first necessary to prepare sulfone 14. This was
accomplished as shown in Scheme 3. Reduction of the
lactol 2 to the corresponding diol 11 was achieved using
sodium borohydride in methanol at 0 °C. The primary
hydroxy group of 11 was converted selectively into the
1-phenyl-1H-tetrazol-5-yl thioether 12 under Mitsunobu
conditions.19 Protection of the two hydroxyl functions of
(20) (a) Baudin, J . B.; Hareau, G.; J ulia, S. A.; Ruel, O. Tetrahedron
Lett. 1991, 32, 1175-1178. (b) Baudin, J . B.; Hareau, G.; J ulia, S. A.;
Ruel, O. Bull. Soc. Chim. Fr. 1993, 130, 336-357. (c) Baudin, J . B.;
Hareau, G.; J ulia, S. A.; Lorne, R.; Ruel, O. Bull. Soc. Chim. Fr. 1993,
130, 856-878.
(21) J ulia, M.; Paris, J .-M. Tetrahedron Lett. 1973, 4833-4836.

Synthesis of Sanglifehrin A
J . Org. Chem., Vol. 64, No. 26, 1999 9635
12 using TESOTf22,23 led to the bissilyl ether 13. Oxida-
tion of 13 with 5 equiv of mCPBA in methylene chloride
afforded sulfone 14.24 The overall yield for the four-step
sequence leading from 2 to 14 was 47%.
Sch em e 4a
With the aldehyde 5, its silylated variant 6, and the
sulfone 14 in hand, we were in a position to investigate
the reconstruction of sanglifehrin A (1). Initial attempts
at coupling aldehyde 6 and sulfone 14 using the J ulia-
Kocienski olefination procedure were hampered by the
fact that this particular sulfone quickly decomposed upon
R-metalation with NaHMDS at low temperature. We
therefore envisaged to carry out the reaction in a Barbier-
type fashion, i.e., by adding the base to a mixture of the
aldehyde 6 and the sulfone 14. Unfortunately, this
procedure only resulted in the recovery of starting
materials.25 Reasoning that the presence of rather bulky
silyl protecting groups in both coupling partners might
be retarding the reaction, we decided to attempt the
coupling using aldehyde 5, which lacks a protecting group
on the phenol. In the event, deprotonation of the sulfone
14 using NaHMDS in DME at -78 °C in the presence of
the unsaturated aldehyde 5, followed by quenching of the
reaction at -78 °C,26 resulted in the formation of the E,E
diene 15 as the only detectable product (Scheme 4).28,29
The desired condensation product was accompanied by
unreacted starting materials. Considering the complexity
of the two fragments which are coupled, the 49% yield of
15 obtained after purification and the high E selectivity30
are notable. It is worth mentioning that the use of 2 equiv
of NaHMDS proved optimal for carrying out the olefina-
a
Reagents and conditions: (a) 2 equiv of NaHMDS, DME, -78
°C, 8 h; (b) 5 equiv of Bu4NF, THF, 0 °C to rt, 3 days; (c) 1 equiv
of TsOH, 5 equiv of B(OH)3, THF, rt, 5 h.
tion, despite the presence of one amino NH, three amidic
NH’s, and an unprotected phenol in the substrates.
Having achieved the critical coupling step, further trans-
formation of 15 into 1 was relatively straightforward. The
removal of the two triethylsilyl protecting groups in 15
proceeded very efficiently.31 Finally, acidic hydrolysis of
the intramolecular ketal of 16 furnished sanglifehrin A
(1) (Scheme 4).32 The spectral and chromatographic
characteristics of the hemisynthetic material were identi-
cal in all respects to those of an authentic sample of
sanglifehrin A.7b
In conclusion, we have been able to selectively and
efficiently cleave sanglifehrin A (1) into the fragments 2
and 3. These fragments could be used to investigate the
endgame of a total synthesis of 1. We have indeed
demonstrated that subunits derived from 2 and 3,
namely, aldehyde 5 and sulfone 14, can be reassembled
to intermediate 15, which after two deprotection steps
affords sanglifehrin A (1). Application of the recently
described J ulia-Kocienski olefination procedure proved
to be crucial for our approach. The results described
herein make the aldehyde 5 and the sulfone 14 very
attractive subtargets for a total synthesis of sanglifehrin
A. Furthermore, each of these two subunits can be used
for the synthesis of sanglifehrin analogues which could
not be obtained by simple derivation of the natural
product. For example, the replacement of the spirobicyclic
system by simpler moieties can be envisaged, as is
demonstrated by the reaction shown in eq 2. Alterna-
tively, the sulfone 14 could be coupled with synthetic
analogues of the sanglifehrin macrocycle. Work along
(22) Heathcock, C. H.; Young S. D.; Hagen J . P.; Pilli, R.; Bad-
ertscher, U. J . Org. Chem. 1985, 50, 2095-2105.
(23) The use of triethylsilyl chloride led to selective monoprotection
of the C31-hydroxyl.
(24) When smaller amounts of mCPBA were used, a mixture of
sulfone and sulfoxide was obtained.
(25) The Barbier-type J ulia-Kocienski olefination between 14 or
related sulfones, bearing other hydroxyl protecting groups, and 3-phe-
nylpropionaldehyde proceeded in acceptable yields.
(26) Allowing the reaction mixture to warm to room temperature,
as recommended in ref 19, resulted in displacement of the alkylsulfonyl
moiety of 14 by the sodium phenoxide of 15, resulting in the formation
of significant amounts of the O-(1-phenyl-1H-tetrazol-5-yl) derivative
of 15, as shown below.
For examples of the displacement of alkylsulfonyl moieties from alkyl
tetrazolyl sulfones by alkoxides, see ref 27.
(27) (a) Gol’tsberg, M. A.; Koldobskii, G. I. Zh. Org. Khim. 1995,
31, 1726-1727. (b) Gol’tsberg, M. A.; Koldobskii, G. I. Zh. Org. Khim.
1996, 32, 1238-1245.
(30) Recently a case has been described in which the use of 1-phenyl-
1H-tetrazol-5-yl sulfones resulted in low E selectivity or even in
preferential formation of the Z alkene: Williams, D. R.; Clark, M. P.
Tetrahedron Lett. 1999, 40, 2291-2294.
(31) Corey, E. J .; Venkateswarlu, A. J . Am. Chem. Soc. 1972, 94,
6190-6191.
(28) In contrast to the lack of selectivity observed in their reactions
with aliphatic aldehydes, R-lithiated benzothiazol-2-yl sulfones have
been reported to give high
E selectivities with R,â-unsaturated
aldehydes. For examples in natural product syntheses, see: (a) Smith,
N. D.; Kocienski, P. J .; Street, S. D. A. Synthesis 1996, 652-666. (b)
Bellingham, R.; J arowicki, K.; Kocienski, P.; Martin, V. Synthesis 1996,
285-296. In our case, however, the yield and selectivity were much
lower when the benzothiazol-2-yl sulfone analogue of 14 was employed.
(29) Recent applications of the J ulia-Kocienski olefination in
natural product synthesis: Herboxidiene: (a) Blakemore, P. R.;
Kocienski, P. J .; Morley, A.; Muir, K. J . Chem. Soc., Perkin Trans. 1,
1999, 955-968. Hennoxazole A: (b) Williams, D. R.; Brooks, D. A.;
Berliner, M. A. J . Am. Chem. Soc. 1999, 121, 4924-4925.
(32) The acidic hydrolysis of the intramolecular ketal subunit of 16
to afford 1 stops at approximately 40-50% conversion. The yield given
is for pure sanglifehrin A after HPLC purification. Despite extensive
efforts, we were not able to improve this deprotection step. The addition
of boric acid slightly increases conversions with respect to reactions
performed in its absence. Furthermore, it allows side reactions which
readily occur in aqueous acidic conditions and which are going to be
reported elsewhere to be prevented. The beneficial effect of boric acid
is presumably due to in situ trapping of the 1,3-diol function of 1 as
the corresponding borate.

9636 J . Org. Chem., Vol. 64, No. 26, 1999
Metternich et al.
these lines, as well as efforts toward the total synthesis
of sanglifehrin A (1), are currently underway in our
laboratories and are going to be reported in due course.
(d, J ) 7.7 Hz, 1H), 6.49 (s, 1H), 6.14 (dd, J ) 10.7, 14.9
Hz, 1H), 6.02 (dd, J ) 10.7, 14.9 Hz, 1H), 5.58 (m, 4H),
5.33 (m, 2H), 5.19 (m, 1H), 4.76 (d, J ) 4.9 Hz, 1H), 4.58
(d, J ) 4.3 Hz, 1H), 4.46 (d, J ) 11.5 Hz, 1H), 4.32 (d, J
) 4.5 Hz, 1H), 4.18 (m, 1H), 4.07 (t, J ) 8.9 Hz, 1H),
3.96 (d, J ) 5.6 Hz, 1H), 3.93 (m, 2H), 3.81 (m, 1H), 3.69
(t, J ) 9.8 Hz, 1H), 3.55 (m, 1H), 3.43 (m, 1H), 3.18 (m,
1H), 2.83-2.33 (m, 7H), 2.11-1.72 (m, 9H), 2.05 (s, 3H),
1.64 (s, 3H), 1.63-1.18 (m, 16H), 0.89 (m, 6H), 0.82 (m,
12H), 0.72 (d, J ) 6.4 Hz, 3H), 0.59 (d, J ) 6.8 Hz, 3H);
13C NMR (125 MHz, DMSO-d6)34 δ 208.4, 175.0, 174.4,
172.2, 171.1, 170.5, 157.7, 138.6, 135.2, 135.1, 134.7,
131.5, 130.9, 130.3, 130.1, 128.3, 120.4, 117.0, 113.6, 87.1,
77.2, 74.7, 74.6, 73.6, 71.6, 70.9, 70.8, 66.8, 58.1, 57.8,
51.7, 40.9, 40.7, 37.9, 37.5, 36.7, 30.4, 30.2, 29.0, 28.7,
27.7, 25.8, 22.8, 19.7, 18.8, 15.2, 14.8, 14.5, 13.7, 13.4,
12.3, 11.3; Rf 0.43 (85:15 methyl tert-butyl ether/
methanol, HPTLC plate); HRMS calcd for C60H93N5NaO15
[M + Na]+ requires 1146.6566, found 1146.6558.
Exp er im en ta l Section
Gen er a l P r oced u r es. Dry THF, acetonitrile, meth-
ylene chloride, and diethyl ether (puriss., absolute, over
molecular sieves) were purchased from Fluka in septum-
capped bottles and were used as such. All reactions were
performed under an atmosphere of argon. Sanglifehrin
A was obtained from Novartis Pharma Research, Core
Technology Area, Biomolecules Production, Basel, Swit-
zerland. Osmium tetroxide (2.5 wt % solution in tert-butyl
alcohol), (DHQ)2PHAL, and (DHQD)2PHAL were pur-
chased from Aldrich. Sodium bis(trimethylsilyl) amide
was titrated with 2,6-di-tert-butyl-4-methylphenol in THF
using fluorene as an indicator.32 Analytical thin-layer
chromatography (TLC) was performed on precoated silica
gel 60 F254 plates or on precoated HPTLC silica gel 60
F254 plates with concentrating zone (Merck). HPLC
analyses were performed at 40 °C using a Merck LiChro-
CART 125-4 cartridge packed with LiChrospher 100 RP-
18 (5 µm). Gradients consisting of mixtures of solvent A
(acetonitrile:water ) 1:9) and solvent B (acetonitrile:
water ) 9:1) or of mixtures of acetonitrile and water were
used. The flow rate was 1.5 mL/min. Detection was
performed at 210 nm. Purification by flash chromatog-
raphy was performed using Merck silica gel 60 (230-
400 mesh). Reversed phase HPLC purifications were
performed at 25 °C using a Macherey-Nagel 250/10
Nucleosil 100-7 C18 column. The elution system consisted
of 10:90-90:10 acetonitrile/water over 2.5 min, followed
by 10:90-90:10 acetonitrile/water (linear gradient over
20 min) and finally 90:10 acetonitrile/water over 7.5 min.
The flow rate was 10-12.5 mL/min. Detection was per-
formed at 214 and 254 nm.
26(S),27(S)-Dih ydr oxysan glifeh r in A (4). To a stirred
solution of 21.80 g (20.00 mmol) of sanglifehrin A, 0.934
g (1.20 mmol) of (DHQ)2PHAL, 7.5 mL (0.60 mmol) of a
2.5 wt % solution of osmium tetroxide in tert-butyl
alcohol, and 3.80 g (39.95 mmol) of methanesulfonamide
in 100 mL of tert-butyl alcohol were added, at room
temperature, a solution of 19.70 g (59.84 mmol) of
potassium ferricyanide and 8.30 g (60.06 mmol) of
potassium carbonate in 100 mL of water, resulting in a
brown emulsion. After 2 h a solution of 30.00 g (238.10
mmol) of sodium sulfite was added, and stirring was
continued for 10 min. The resulting mixture was ex-
tracted with three portions of ethyl acetate. The organic
solution was washed with four portions of saturated
brine. After the combined aqueous layers were extracted
with an additional portion of ethyl acetate, the combined
organic extracts were dried over anhydrous sodium
sulfate, filtered, and concentrated under reduced pres-
sure. The residue was purified by column chromatogra-
phy on silica gel (85:15 methyl tert-butyl ether/methanol)
to afford 15.65 g (70%) of 4 as an amorphous white solid.
This material was 95.3% pure by HPLC analysis (80:20-
0:100 solvent A/solvent B, linear gradient over 20 min,
tR 7.3 min): [R]20D ) -34.1 (c 1.0, CH2Cl2); IR (KBr) 3387,
1714, 1644 cm-1; 1H NMR (500 MHz, DMSO-d6)34 δ 9.24
(s, 1H), 8.14 (d, J ) 6.4 Hz, 1H), 7.89 (s, 1H), 7.52 (d, J
) 9 Hz, 1H), 7.06 (t, J ) 7.8 Hz, 1H), 6.58 (m, 1H), 6.54
Oxid a tive Clea va ge of th e Diol 4 to th e La ctol 2
a n d th e Ma cr ocyclic Ald eh yd e 3. To a solution of 7.42
g (6.60 mmol) of diol 4 in 75 mL of a 2:1 mixture of THF
and water was added 2.82 g (13.18 mmol) of sodium
periodate. The resulting mixture was stirred at room
temperature for 1 h, and saturated aqueous sodium
bicarbonate was added. This mixture was extracted with
three portions of ethyl acetate. The combined organic
layers were washed with one portion of water and two
portions of saturated brine, dried over anhydrous sodium
sulfate, filtered, and concentrated under reduced pres-
sure. The residue was purified by column chromatogra-
phy on silica gel (95:5-90:10 methyl tert-butyl ether/
methanol) to afford 2.19 g (87%) of lactol 2 and 4.24 g
(87%) of the aldehyde 3 as white amorphous solids.
Purities, as determined by HPLC analysis, were 98.6%
for 2 (20:80-100:0 acetonitrile/water, linear gradient over
20 min, tR 11.7 min) and 97.4% for 3 (20:80-100:0
acetonitrile/water, linear gradient over 20 min, tR 5.1
min).
Da ta for 2: [R]20 ) -91.0 (c 1.0, CH2Cl2); IR (KBr)
D
1
3301, 1618, 1469 cm-1; H NMR (400 MHz, DMSO-d6)
(∼1:1 mixture of anomers) δ 7.92 and 7.91 (2s, 1H), 5.98
(d, J ) 6.4 Hz, 0.5H), 5.63 (d, J ) 5.5 Hz, 0.5H), 5.61 (d,
J ) 5.3 Hz, 0.5H), 5.42 (d, J ) 4.3 Hz, 0.5H), 4.96 (s,
0.5H), 4.38 (m, 0.5H), 4.09 (m, 0.5H), 3.67(m, 1H), 3.58
(m, 1.5H), 2.16-1.86 (m, 3H), 1.81-1.13 (m, 12H), 0.99-
0.73 (m, 15H); 13C NMR (125 MHz, DMSO-d6) (∼1:1
mixture of anomers) δ 175.1, 175.2, 96.9, 90.3, 87.5, 87.4,
74.6, 73.6, 67.8, 66.8, 66.5, 41.0, 40.9, 40.8, 40.7, 37.5,
(34) Sanglifehrin A (1) and derivatives containing the macrocyclic
subunit exist as an approximately 4:1:1 mixture of isomers in solution
in DMSO-d6. One of the isomers probably arises from the ketone-
diol:hemiketal equilibrium shown below.
Evidence for this equilibrium is provided by the presence of a minor
signal at approximately 95 ppm in the 13C spectra of these compounds.
The third isomer is presumably an amide bond rotamer. Only the
signals corresponding to the major isomer are listed.
(33) Brown, C. A. Synthesis 1974, 427-428.

Synthesis of Sanglifehrin A
J . Org. Chem., Vol. 64, No. 26, 1999 9637
37.4, 36.6, 35.8, 31.2, 30.6, 30.4, 30.1, 29.0, 28.8, 28.3,
26.4, 26.0, 25.9, 25.5, 15.1, 14.5, 14.4, 13.3, 12.4, 0.12.3,
12.2, 12.1; Rf 0.62 (95:5 methyl tert-butyl ether/methanol,
HPTLC plate); HRMS calcd for C21H37NNaO5 [M + Na]+
requires 406.2569, found 406.2567. Anal. Calcd for
C21H37NO5: C, 65.77; H, 9.72; N, 3.65. Found: C, 65.56;
H, 9.78; N, 3.62.
ether/methanol, HPTLC plate); HRMS calcd for C39H52N4-
NaO9 (M + Na) requires 743.3632, found 743.3634.
TBDMS-P r otected Keta l-a ld eh yd e 6. A solution of
1.35 g (1.87 mmol) of 5 and 0.52 mL (2.25 mmol) of
MTBSTFA in 15 mL of dry acetonitrile was heated to 50
°C for 1.5 h. After the solution was cooled to cool to room
temperature, saturated aqueous sodium bicarbonate was
added. The resulting mixture was extracted three times
with ethyl acetate. The combined organic layers were
washed twice with saturated brine, dried over anhydrous
sodium sulfate, filtered, and concentrated under reduced
pressure. The residue was purified by column chroma-
tography on silica gel (95:5 methyl tert-butyl ether/
methanol) to afford 6 (1.37 g, 88%) as a white amorphous
solid. The purity of the compound was 94.5% according
to HPLC analysis (50:50-0:100 solvent A/solvent B,
Da ta for 3: [R]20 ) +10.4 (c 1.0, CH2Cl2); IR (KBr)
D
3369, 1740, 1715, 1641 cm-1; 1H NMR (500 MHz, DMSO-
d6)34 δ 9.98 (d, J ) 7.9 Hz, 1H), 9.26 (s, 1H), 8.17 (d, J )
7.0 Hz, 1H), 7.52 (d, J ) 9.0 Hz, 1H), 7.05 (t, J ) 7.8 Hz,
1H), 6.58 (m, 2H), 6.51 (s, 1H), 6.16 (dd, J ) 10.7, 14.8
Hz, 1H), 6.08 (dd, J ) 10.7, 14.8 Hz, 1H), 5.87 (d, J )
7.7 Hz, 1H), 5.60 (m, 2H), 5.39 (m, 2H), 5.32 (dd, J )
1.6, 9.0 Hz, 1H), 4.78 (d, J ) 4.7 Hz, 1H), 4.62 (d, J )
12.0 Hz, 1H), 4.19 (m, 1H), 4.09 (t, J ) 8.7 Hz, 1H), 3.97
(m, 1H), 3.79 (m, 1H), 2.77-2.33 (m, 7H), 2.16 (s, 3H),
2.14 (m, 1H), 2.05 (s, 3H), 1.87 (m, 1H), 1.75 (m, 3H),
1.61 (m, 2H), 1.35 (m, 3H), 0.80 (d, J ) 6.8 Hz, 6H), 0.61
linear gradient over 20 min, tR 9.8 min): [R]20 ) + 11.7
D
(c 1.0, CH2Cl2); IR (KBr) 3326, 1682, 1512, 841 cm-1; 1H
NMR (DMSO-d6, 500 MHz)35 δ 9.95 (d, J ) 7.7 Hz, 1H),
8.45 (d, J ) 7.3 Hz, 1H), 7.00 (t, J ) 7.9 Hz, 1H), 6.70
(m, 2H), 6.61 (d, J ) 8.1 Hz, 1H), 6.58 (s, 1H), 6.13 (dd,
J ) 10.5, 15.2 Hz, 1H), 6.02 (dd, J ) 10.6, 15.3 Hz, 1H),
5.87 (d, J ) 7.7 Hz, 1H), 5.68 (dt, J ) 6.4, 15.2 Hz, 1H),
5.54 (dd, J ) 7.5, 15.0 Hz, 1H), 5.32 (dd, J ) 3.3, 9.3 Hz,
1H), 5.17 (dd, J ) 7.7, 15.2 Hz, 1H), 5.04 (d, J ) 12.0
Hz, 1H), 4.55 (dd, J ) 7.9, 11.1 Hz, 1H), 4.24 (m, 2H),
4.17 (t, J ) 4.7 Hz, 1H), 2.85 (m, 2H), 2.67 (m, 3H), 2.48
(m, 2H), 2.33 (m, 1H), 2.12 (s, 3H), 1.96 (m, 3H), 1.81
(m, 2H), 1.69 (m, 1H), 1.52 (m, 2H), 1.33 (m, 1H), 1.19
(s, 3H), 0.93 (s, 9H), 0.86 (d, J ) 6.6 Hz, 3H), 0.75 (d, J
(d, J ) 7.0 Hz, 2H); 13C NMR (125 MHz, DMSO-d6)34
δ
208.4, 192.5, 174.8, 172.3, 170.8, 170.5, 160.2, 157.7,
138.8, 135.2, 132.3, 130.4, 130.2, 128.6, 125.5, 120.5,
117.0, 113.6, 75.8, 74.6, 72.0, 58.2, 57.7, 51.7, 49.2, 43.8,
40.9, 40.8, 38.9, 36.0, 30.6, 30.4, 27.6, 26.2, 22.8, 19.7,
18.8, 14.5, 14.3, 11.2; Rf 0.66 (90:10 methyl tert-butyl
ether/methanol, HPTLC plate); HRMS calcd for C39H54N4-
NaO10 [M + Na]+ requires 761.3737, found 761.3740.
Keta l-Ald eh yd e 5. To a stirred, cooled (0 °C) solution
of 2.96 g (2 mmol) of 3 in 25 mL of acetonitrile was added
2.5 mL of HF-pyridine complex. The yellow solution was
stirred at 0 °C for 1 h. The reaction was quenched with
saturated aqueous sodium bicarbonate, and the resulting
mixture was extracted with three portions of ethyl
acetate. The combined organic layers were washed once
with saturated aqueous sodium bicarbonate and twice
with brine, dried over sodium sulfate, and concentrated
under reduced pressure. The crude product was purified
by flash chromatography on silica gel (95:5 methyl tert-
butyl ether/methanol) to afford 5 (2.66 g, 92%) as a white
amorphous solid. The purity of the compound was 96.1%
according to HPLC analysis (30:70-70:30 acetonitrile/
) 6.8 Hz, 3H), 0.30 (d, J ) 7.5 Hz, 3H), 0.16 (s, 6H); 13
C
NMR (DMSO-d6, 125 MHz)35 δ 192.3, 172.2, 170.8, 170.7,
170.4, 159.6, 155.3, 139.3, 134.6, 131.0, 130.9, 130.5,
129.9, 125.7, 122.4, 121.5, 117.6, 95.7, 80.2, 75.8, 73.2,
60.2, 59.3, 56.7, 49.5, 44.0, 39.0, 38.1, 35.0, 34.2, 31.3,
29.5, 26.9, 26.0, 23.0, 22.9, 21.2, 19.8, 18.3, 18.0, 14.5,
14.4, 12.2, -4.1, -4.2; Rf 0.59 (95:5 methyl tert-butyl
ether/methanol, HPTLC plate); HRMS calcd for C45H66N4-
NaO9Si (M + Na) requires 857.4497, found 857.4496.
Tr iol 11. To a stirred, cooled (0 °C) solution of 100 mg
(0.26 mmol) of lactol 2 in 2 mL of methanol was added a
solution of 30 mg (0.78 mmol) of sodium borohydride in
1 mL of methanol. The reaction mixture was stirred at 0
°C for 2 h and quenched with a saturated aqueous
ammonium chloride solution and water. The aqueous
layer was extracted with ethyl acetate. The combined
organic layers were washed with brine, dried over sodium
sulfate, and concentrated under reduced pressure. The
crude product was purified by crystallization in n-hexane
to afford 93.2 mg (93%) of 11 as white crystals. The purity
of the compound was 95.3% according to HPLC analysis
(10:90-50:50 acetonitrile/water, linear gradient over 4
min, and then 50:50-100:0 acetonitrile/water, linear
water, linear gradient over 15 min, tR 4.2 min): [R]20
)
D
+128.0 (c 1.0, CH2Cl2); IR (KBr) 3385, 1670, 1511, 1161
cm-1; 1H NMR (DMSO-d6, 500 MHz)35 δ 9.96 (d, J ) 7.7
Hz, 1H), 9.22 (s, 1H), 8.44 (d, J ) 7.5 Hz, 1H), 6.92 (t, J
) 7.7 Hz, 1H), 6.70 (d, J ) 9.2 Hz, 1H), 6.54 (d, J ) 7.0
Hz, 1H), 6.48 (m, 2H), 6.15 (dd, J ) 10.6, 15.0 Hz, 1H),
6.04 (dd, J ) 10.6, 15.2 Hz, 1H), 5.87 (d, J ) 4 Hz, 1H),
5.66 (dt, J ) 6.5, 15.2 Hz, 1H), 5.54 (dd, J ) 7.5, 15.4
Hz, 1H), 5.35 (dd, J ) 3.1, 9.4 Hz, 1H), 5.20 (dd J ) 7.9,
15.2 Hz, 1H), 4.92 (d, J ) 12.2 Hz, 1H), 4.55 (dd, J )
8.1, 10.9 Hz, 1H), 4.25 (m, 2H), 4.19 (t, J ) 4.7 Hz, 1H),
2.87 (m, 1H), 2.76 (m, 1H), 2.65 (m, 2H), 2.55 (m, 2H),
2.35 (m, 1H), 2.25 (m, 1H), 2.14 (s, 3H), 2.03 (m, 2H),
1.91 (m, 2H), 1.80 (m, 1H), 1.66 (m, 1H), 1.47 (m, 2H),
1.32 (m, 1H), 1.19 (s, 3H), 0.85 (d, J ) 6.6 Hz, 3H), 0.76
(d, J ) 6.6 Hz, 3H), 0.37 (d, J ) 7.5 Hz, 3H); 13C NMR
(DMSO-d6, 125 MHz)35 δ 192.5, 172.3, 170.9, 170.6, 159.7,
157.6, 138.7, 134.8, 131.2, 130.9, 130.5, 129.9, 125.7,
120.0, 117.0, 113.5, 95.7, 80.1, 75.7, 73.2, 59.0, 56.8, 49.3,
44.0, 40.9, 38.9, 38.6, 35.1, 34.2, 31.2, 29.5, 27.0, 23.0,
22.8, 19.8, 18.2, 14.4, 12.3; Rf 0.51 (95:5 methyl tert-butyl
gradient over 6 min, tR 5.6 min): [R]20 ) -84.0 (c 0.5,
D
acetone); mp 42.2-43.2 °C; IR (KBr) 3305, 1647, 1165,
1067 cm-1; 1H NMR (DMSO-d6, 400 MHz) δ 7.91 (s, 1H),
5.59 (d, J ) 4.9 Hz, 1H), 4.32 (t, J ) 5.1 Hz, 1H), 3.99 (d,
J ) 5.5 Hz, 1H), 3.71 (t, J ) 9.8 Hz, 1H), 3.58 (m, 1H),
3.50 (m, 1H), 3.36 (m, 2H), 2.07 (m, 1H), 1.93 (m, 2H),
1.75 (m, 1H), 1.64 (m, 1H), 1.56-1.36 (m, 8H), 1.25 (m,
1H), 1.03 (m, 1H), 0.91 (m, 6H), 0.85 (m, 6H), 0.78 (d, J
) 6.7 Hz, 3H); 13C NMR (DMSO-d6, 125 MHz) δ 174.3,
87.1, 73.6, 70.3, 66.9, 61.7, 40.90, 40.76, 39.12, 37.94,
37.49, 30.97, 30.45, 29.34, 28.68, 25.77, 15.16, 14.88,
14.55, 13.41, 12.36; HRMS calcd for C21H39NNaO5 (M +
Na) requires 408.2726, found 408.2727. Anal. Calcd for
(35) Derivatives such as 16, containing the intramolecular ketal
substructure, exist as an approximately 10:1 mixture of isomers in
solution in DMSO-d6. Only the signals corresponding to the major
isomer are listed.

9638 J . Org. Chem., Vol. 64, No. 26, 1999
Metternich et al.
C21H39NO5 C, 65.42; H, 10.20; N, 3.63. Found: C, 65.22;
H, 10.32; N, 3.66.
277.5 mg (1.6 mmol) of mCPBA in 2 mL of dichlo-
romethane. The reaction mixture was stirred at room
temperature for 14 h and quenched by addition of
saturated aqueous sodium bicarbonate and saturated
aqueous sodium thiosulfate. The aqueous layer was
extracted with ethyl acetate. The combined organic layers
were washed with brine, dried over sodium sulfate,
filtered, and concentrated under reduced pressure. The
residue was purified by column chromatography on silica
gel (70:30 hexane/ethyl acetate) to afford 252.8 mg (98%)
of 14 as a colorless oil. The purity of the compound was
100% according to HPLC analysis (70:30-100:00 aceto-
nitrile/water, linear gradient over 10 min, and then
Su lfid e 12. To a stirred, cooled (0 °C) solution of 102.10
mg (0.57 mmol) of 1-phenyl-1H-tetrazole-5-thiol and
150.27 mg (0.57 mmol) of triphenylphosphine in 5 mL of
THF was added via cannula a solution of 200.8 mg (0.52
mmol) of 11 in 2 mL of THF. Then, 0.11 mL (0.57 mmol)
of diisopropyl azodicarboxylate was added dropwise over
10 min. The resulting mixture was allowed to warm to
room temperature and stirred for 30 h. The solvents were
removed under reduced pressure, and the crude product
was purified by HPLC, using the elution system de-
scribed in the General Procedures, to afford 201.5 mg
(71%) of 12 (tR 18.8 min) as a white solid. The purity of
the compound was 97.4% according to HPLC analysis (10:
90-100:00 acetonitrile/water, linear gradient over 5 min,
acetonitrile over 6 min, tR 11.0 min): [R]20 ) -43.0 (c
D
1
1.0, acetone); IR (film) 3351, 1347, 1154 cm-1; H NMR
(DMSO-d6, 400 MHz) δ 7.71 (m, 5H), 7.57 (s, 1H), 3.87
(s, 1H), 3.77 (m, 3H), 3.64 (t, J ) 10.2 Hz, 1H), 1.93 (m,
3H), 1.84 (m, 2H), 1.67 (m, 3H), 1.44 (m, 5H), 1.27 (m,
1H), 1.10 (m, 1H), 0.99 (t, J ) 7.9 Hz, 9H), 0.88 (m, 21H),
0.76 (d, J ) 6.6 Hz, 3H), 0.66 (m, 6H), 0.50 (m, 6H); 13C
NMR (DMSO-d6, 125 MHz) δ 173.7, 153.9, 133.4, 132.0,
129.9, 126.7, 86.9, 77.4, 72.9, 66.5, 56.1, 41.6, 40.9, 40.7,
37.8, 37.4, 29.9, 29.7, 28.3, 25.6, 20.6, 15.4, 15.1, 14.8,
13.8, 12.6, 7.3, 7.2, 5.3, 5.2; Rf 0.62 (70:30 hexane/ethyl
acetate); HRMS calcd C40H71N5NaO6SSi2 (M + Na)
requires 828.4561, found 828.4564.
and then acetonitrile over 2 min, tR 5.6 min): [R]20
)
D
-16.0 (c 1.0, acetone); IR (KBr) 3288, 1500, 1645, 1500,
1
761, 695 cm-1; H NMR (DMSO-d6, 400 MHz) δ 7.90 (s,
1H), 7.66 (s, 5H), 5.61 (s, 1H), 4.10 (d, J ) 5.5 Hz, 1H),
3.70 (t, J ) 10 Hz, 1H), 3.57 (m, 1H), 3.50 (m, 1H), 3.32
(m, 2H), 2.03 (m, 1H), 1.90 (m, 2H), 1.73 (m, 3H), 1.62-
1.20 (m, 9H), 0.92-0.77 (m, 15H); 13C NMR (DMSO-d6,
125 MHz) δ 174.3, 154.9, 133.6, 131.0, 130.4, 125.0, 87.1,
73.6, 70.0, 66.9, 40.9, 40.8, 39.5, 38.7, 37.5, 33.5, 31.9,
30.4, 28.7, 27.2, 25.8, 15.1, 14.7, 14.5, 13.4, 12.3; Rf 0.33
(98:2 methyl tert-butyl ether/methanol); HRMS calcd
C28H43N5NaO4S (M + Na) requires 568.2933, found
568.2931. Anal. Calcd for C28H43N5O4S C, 61.62; H, 7.94;
N, 12.83. Found: C, 61.27; H, 7.98; N, 12.69.
31,35-Bissilyla ted Sa n glifeh r in A Keta l (15). To a
mixture of 510.3 mg (0.63 mmol) of 14 and 456.2 mg (0.63
mmol) of 5 in 5 mL of ethylene glycol dimethyl ether at
-78 °C was added slowly 2.53 mL (1.27 mmol) of a 0.5
M solution of sodium bis(trimethylsilyl)amide in toluene.
The reaction mixture was stirred at -78 °C for 8 h,
quenched with saturated aqueous sodium bicarbonate,
and diluted with water. The resulting mixture was
extracted with ethyl acetate. The combined organic layers
were washed with brine, dried over sodium sulfate, and
concentrated. The crude product was purified by column
chromatography on silica gel (gradient 100% methyl tert-
butyl ether to 95:5 methyl tert-butyl ether/methanol) to
afford 308.9 mg (49%) of 15 as a white amorphous solid.
The purity of the compound was 96.8% according to
HPLC analysis (70:30-100:00 acetonitrile/water, linear
gradient over 4 min, and then acetonitrile over 21min,
Bissilyla ted Su lfid e 13. To a mixture of 1.03 mL of
ether and 0.74 mL of acetonitrile at -20 °C were added
0.098 mL (1.22 mmol) of pyridine and 0.233 mL (1.032
mmol) of triethylsilyl trifluoromethanesulfonate. This
mixture was cooled to -50 °C, and a solution of 256 mg
(0.469 mmol) of 12 in 0.2 mL of acetonitrile was added.
Stirring at -50 °C was continued for 30 min, and the
reaction was quenched with saturated aqueous sodium
bicarbonate. This mixture was diluted with hexane, and
the aqueous layer was extracted with ethyl acetate. The
combined organic layers were washed with brine, dried
over sodium sulfate, and filtered. The solvents were
removed under reduced pressure, and the crude product
was purified by chromatography on silica gel (80:20
hexane/ethyl acetate) to afford 261 mg (72%) of 13 as a
colorless oil. The purity of the compound was 96.6%
according to HPLC analysis (70:30-100:00 acetonitrile/
water, linear gradient over 10 min, and then acetonitrile
over 16 min, tR 13.1 min): [R]20D ) -62.0 (c 1.0, acetone);
IR (film) 3352, 1667, 1069, 1007 cm-1; 1H NMR (DMSO-
d6, 400 MHz) δ 7.66 (m, 5H), 7.56 (s, 1H), 3.86 (s, 1H),
3.74 (d, J ) 7.4 Hz, 1H), 3.64 (t, J ) 10.3 Hz, 1H), 3.36
(m, 2H), 1.94 (m, 3H), 1.83 (m, 2H), 1.64 (m, 3H), 1.45
(m, 5H), 1.28 (m, 1H), 1.10 (m, 1H), 0.98 (t, J ) 7.9 Hz,
9H), 0.92-0.81 (m, 21H), 0.78 (d, J ) 6.9 Hz, 3H), 0.66
(m, 6H), 0.48 (m, 6H); 13C NMR (DMSO-d6, 125 MHz) δ
173.7, 154.8, 133.5, 131.0, 130.4, 124.9, 86.9, 77.4, 72.9,
66.6, 41.6, 40.9, 40.5, 37.8, 37.6, 33.5, 30.1, 29.9, 28.3,
27.6, 25.6, 15.4, 15.1, 14.8, 13.8, 12.6, 7.3, 5.3, 5.2; Rf 0.45
(80:20 hexane/ethyl acetate); HRMS calcd C40H71N5NaO4-
SSi2 (M + Na) requires 796.4663, found 796.4651. Anal.
Calcd for C40H71N5O4SSi2 C, 62.05; H, 9.24; N, 9.05.
Found: C, 61.97; H, 9.10; N, 8.91.
tR 11.9 min): [R]20 ) -35.0 (c 2.0, acetone); IR (KBr)
D
1
3352, 1736, 1648, 1506, 990 cm-1; H NMR (DMSO-d6,
400 MHz)35 δ 9.23 (s, 1H), 8.48 (d, J ) 9.0 Hz, 1H), 7.57
(s, 1H), 6.96 (t, J ) 6.3 Hz, 1H), 6.73 (d, J ) 7.8 Hz, 1H),
6.57 (d, J ) 8.0 Hz, 1H), 6.49 (m, 2H), 6.19 (m, 2H), 6.03
(m, 2H), 5.95 (m, 3H), 5.29 (d, J ) 11.0 Hz, 1H), 5.20
(dd, J ) 7.6, 14.8 Hz, 1H), 4.82 (d, J ) 11. 0 Hz, 1H),
4.58 (dd, J ) 8.4, 9.2 Hz, 1H), 4.23 (m, 3H), 3.86 (s, 1H),
3.75 (m, 1H), 3.65 (m, 1H), 2.90 (m, 1H), 2.72 (m, 2H),
2.56 (m, 3H), 2.35 (m, 1H), 2.19 (m, 2H), 1.92 (m, 10H),
1.70 (s, 3H), 1.67 (m, 2H), 1.47 (m, 8H), 1.21 (s, 3H), 1.20
(m, 3H), 1.01-0.71 (m, 39H), 0.66 (m, 6H), 0.50 (m, 6H),
0.40 (d, J ) 8.0 Hz, 3H); 13C NMR (DMSO-d6, 125 MHz)
δ 173.7, 172.3, 170.9, 170.6, 157.6, 138.6, 136.3, 134.9,
132.1, 130.4, 130.3, 130.2, 130.0, 129.8, 126.6, 126.1,
120.0, 117.0, 113.5, 95.6, 86.9, 80.0, 77.5, 73.2, 73.0, 66.6,
59.2, 56.9, 49.2, 44.0, 41.6, 40.9, 40.8, 39.2, 38.9, 38.8,
37.8, 37.6, 35.8, 34.2, 31.2, 31.0, 30.9, 29.9, 29.5, 28.3,
27.0, 25.6, 23.0, 22.8, 19.8, 18.2, 15.3, 15.1, 14.8, 13.8,
13.1, 12.6, 12.4, 7.3, 5.3, 5.2, 5.1; Rf 0.40 (98:2 methyl
tert-butyl ether/methanol); HRMS calcd C72H117N5NaO12-
Si2 (M + Na) requires 1322.8135, found 1322.8125.
Su lfon e 14. To a solution of 249.0 mg (0.32 mmol) of
13 in 4 mL of dichloromethane was added 270.2 g (3.2
mmol) of sodium bicarbonate followed by a solution of

Synthesis of Sanglifehrin A
J . Org. Chem., Vol. 64, No. 26, 1999 9639
Sa n glifeh r in A Keta l (16). To a solution of 155.5 mg
(0.12 mmol) of 15 in 2 mL of tetrahydrofuran at 0 °C was
added 0.6 mL (0.6 mmol) of a 1 M solution of TBAF in
THF. The resulting solution was stirred at room tem-
perature for 3 days. After evaporation of the solvent
under reduced pressure, the residue was diluted with
ethyl acetate and acidified to pH 1. The layers were
separated, and the aqueous layer was extracted with
ethyl acetate. The combined organic layers were washed
with brine, dried over sodium sulfate, and filtered, and
the solvents were removed under reduced pressure. The
residue was purified by column chromatography on silica
gel to afford 102.7 mg (80%) of 16 as a white amorphous
solid. The purity of the compound was 93.8% according
to HPLC analysis (10:90-100:00 acetonitrile/water, lin-
bicarbonate solution. The mixture was extracted three
times with ethyl acetate. The combined organic layers
were washed with brine, dried over anhydrous sodium
sulfate, and concentrated under reduced pressure. The
crude product was purified by preparative HPLC, using
the conditions described in the General Procedures, to
afford 62.2 mg (30%) of sanglifehrin A (1) (tR 22.8 min)
along with 42.9 mg (20%) of recovered 16 (tR 24.1 min).
The purity of the compound was 97.5% according to
HPLC analysis (10:90-100:00 acetonitrile/water, linear
gradient over 8 min, and then acetonitrile over 2 min, tR
7.2 min). Hemisynthetic sanglifehrin A (1) exhibited the
following characteristics: 1H NMR (DMSO-d6, 400 MHz)34
δ 9.28 (s, 1H), 8.16 (d, J ) 6.5 Hz, 1H), 7.91 (s, 1H), 7.54
(d, J ) 9.0 Hz, 1H), 7.08 (t, J ) 7.7 Hz, 1H), 6.61 (d, J )
7. 0 Hz, 1H), 6.58 (d, J ) 7.2 Hz, 1H), 6.52 (s, 1H), 6.11
(m, 4H), 5.65 (m, 3H), 5.61 (d, J ) 4.5 Hz, 1H), 5.50 (m,
1H), 5.38 (m, 1H), 5.25 (d, J ) 9.4 Hz, 1H), 4.80 (d, J )
3.5 Hz, 1H), 4.52 (d, J ) 11.4 Hz, 1H), 4.19 (m, 1H), 4.12
(m, 1H), 4.06 (d, J ) 5.1 Hz, 1H), 3.92 (m, 1H), 3.83 (m,
1H), 3.71 (t, J ) 9.58 Hz, 1H), 3.58 (m, 1H), 3.53 (m, 1H),
2.78-2.23 (m, 7H), 2.10 (m, 4H), 2.07 (s, 3H), 1.93 (m,
4H), 1.78-1.13 (m, 17H), 1.71 (s, 3H), 0.93-0.79 (m,
21H), 0.62 (d, J ) 6.7 Hz, 3H); 13C NMR (DMSO-d6, 125
MHz)34 δ 208.4, 174.9, 174.3, 172.2, 171.1, 170.5, 157.7,
138.7, 136.5, 134.7, 133.2, 131.6, 130.8, 130.2, 130.0,
126.4, 125.9, 120.4, 117.0, 113.6, 87.1, 77.5, 74.6, 73.6,
71.8, 69.9, 66.9, 58.2, 57.8, 51.7, 49.2, 40.9, 40.8, 38.9,
38.7, 38.1, 37.5, 36.6, 32.8, 30.6, 30.5, 30.4, 30.3, 28.7,
27.7, 25.8, 22.8, 19.7, -17.9, 15.2, 14.6, 14.5, 13.4, 13.2,
12.4, 11.4; HRMS calcd C60H91N5NaO13 (M + Na) requires
1112.65148, found 1112.64975.
ear gradient over 20 min, tR 13.5 min): [R]20 ) -27.0 (c
D
1.0, acetone); IR (KBr) 3500, 3422, 1735, 1648, 985 cm-1
;
1H NMR (DMSO-d6, 400 MHz)35 δ 9.24 (s, 1H), 8.48 (d, J
) 7.6 Hz, 1H), 7.91 (s, 1H), 6.97 (t, J ) 7.9 Hz, 1H), 6.73
(d, J ) 9.0 Hz, 1H), 6.57 (d, J ) 8.2 Hz, 1H), 6.50 (m,
2H), 6.22 (dd, J ) 11.5, 14.7 Hz, 1H), 6.16 (dd, J ) 11.9,
14.5 Hz, 1H), 6.03 (m, 2H), 5.65 (m, 4H), 5.28 (dd, J )
3.0, 10.2 Hz, 1H), 5.20 (dd, J ) 7.8, 15.1 Hz, 1H), 4.82
(d, J ) 12.1 Hz, 1H), 4.69 (m, 1H), 4.24 (m, 3H), 4.07 (d,
J ) 5.5 Hz, 1H), 3.71 (t, J ) 10. 0 Hz, 1H), 3.58 (m, 1H),
3.53 (m, 1H), 2.90 (m, 1H), 2.77 (m, 1H), 2.68 (m, 1H),
2.51 (m, 3H), 2.37 (m, 1H), 2.25-1.92 (m, 10H), 1.75 (m,
2H), 1.70 (s, 3H), 1.65 (m, 2H), 1.57-1.25 (m, 10H), 1.21
(s, 3H), 1.14 (m, 1H), 0.93-0.77 (m, 21H), 0.40 (d, J )
7.2 Hz, 3H); 13C NMR (DMSO-d6, 125 MHz) δ 174.3,
172.3, 171.0, 170.9, 170.6, 157.6, 138.7, 136.6, 134.9,
132.8, 132.1, 130.4, 130.3, 130.0, 126.7, 125.9, 120.0,
117.0, 113.5, 95.6, 87.1, 80.1, 77.5, 73.6, 73.2, 69.9, 66.9,
59.2, 56.9, 49.2, 44.1, 40.9, 40.8, 40.5, 38.9, 38.8, 38.6,
38.0, 37.5, 35.7, 34.2, 32.7, 31.2, 30.6, 30.5, 29.5, 28.7,
27.1, 25.8, 23.0, 22.8, 19.8, 18.2, 15.2, 14.7, 14.5, 13.4,
13.2, 12.4; Rf 0.43 (94:6 methyl tert-butyl ether/methanol);
HRMS calcd C60H89NaN5O12 (M +Na)requires 1094.64091
found 1094.63969.
Ack n ow led gm en t. We thank Drs. Sylvain Cottens,
J u¨rgen Wagner, Mark Burlingame, and Rolf Ba¨nteli for
their contributions to this paper. We thank Lukas
Oberer and J ulien France for their assistance with NMR
analyses, and Charles Quiquerez for the mass spectra.
Su p p or tin g In for m a tion Ava ila ble: Copies of 1H and 13C
NMR spectra for compounds 2-6, 11-16, hemisynthetic
sanglifehrin A (1), and an authentic sample of 1. This material
is available free of charge via the Internet at http://pubs.acs.org.
Sa n glifeh r in A (1). To a solution of 206.3 mg (0.19
mmol) of 16 in 1 mL of THF were added 36.6 mg (0.19
mmol) of TsOH and 59.47 mg (0.96 mmol) of boric acid.
The reaction mixture was stirred at room temperature
for 5 h and quenched with a saturated aqueous sodium
J O9912395