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DOI: 10.1055/s-2003-37506
A New Convergent Approach to Biphenomycin Antibiotics
Publication History
Publication Date:
26 February 2003 (online)
Abstract
A new, convergent approach to the biaryl key intermediate of Schmidt’s biphenomycin B total synthesis has been accomplished via a palladacycle complex catalyzed Stille cross-coupling of two o-tyrosine building blocks.
Key words
biphenomycins - antibiotics - cyclopeptides - asymmetric synthesis - Stille coupling
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1a
Martin JH.Mitscher LA.Shu P.Porter JN.Bohonos N.DeVoe SE.Patterson EL. Antimicrob. Agents Chemother.-1967 1968, 422 -
1b
Chang CC.Morton GO.James JC.Siegel MM.Kuck NA.Testa RT.Borders DB. J. Antibiotics 1991, 44: 674 -
2a
Ezaki M.Iwami M.Yamashita M.Hashimoto S.Komori T.Umehara K.Mine Y.Kohsaka M.Aoki H.Imanaka H. J. Antibiotics 1985, 38: 1453 -
2b
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3a
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Schmidt U.Meyer R.Leitenberger V.Lieberknecht A. Angew. Chem., Int. Ed. Engl. 1989, 28: 929 ; Angew. Chem. 1989, 101, 946 -
4a
Schmidt U.Leitenberger V.Griesser H.Schmidt J.Meyer R. Synthesis 1992, 1248 -
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5a
Schmidt U.Meyer R.Leitenberger V.Griesser H.Lieberknecht A. Synthesis 1992, 1025 -
5b
Schmidt U.Meyer R.Leitenberger V.Lieberknecht A.Griesser H. J. Chem. Soc., Chem. Commun. 1991, 275 - 6 For a recent convergent synthetic
approach to related cyclopeptides, see:
Carbonnelle A.-C.Zhu J. Org. Lett. 2000, 2: 3477 -
7a
Josien H.Martin A.Chassaing G. Tetrahedron Lett. 1991, 32: 6547 -
7b
Oppolzer W.Moretti R.Thomi S. Tetrahedron Lett. 1989, 30: 6009 - 10 The enantiomeric purity of 11 was determined via its Fmoc derivative
by HPLC (ChiraDex®Gamma (5-µm) LiChroCART® 250 × 4
mm (Merck) MeCN-triethylamine-AcOH, 1000:7:0.5,
1 mL/min) according to Armstrong et al. to be > 98% ee.
See:
Tang Y.Zukowski J.Armstrong DW. J. Chromatogr. A 1996, 743: 261 - 11 The absolute configuration of 11 was determined to be S by conversion
into (S)-o-tyrosine,
whose absolute configuration has been unambiguously established.
Lit.:
Dugave C. J. Org. Chem. 1995, 60: 601 - 12
Morera E.Ortar G. Synlett 1997, 1403 - 13
Murata M.Watanabe S.Masuda Y. Synlett 2000, 1043 - 14
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Farina V.Krishnamurthy V.Scott WJ. Org. React. 1997, 50: 1 - 19 For the preparation of 23 (Figure 3), see:
Herrmann WA.Broßmer C.Öfele K.Reisinger C.-P.Priermeier T.Beller M.Fischer H. Angew. Chem., Int. Ed. Engl. 1995, 34: 1844 ; Angew. Chem. 1995, 107, 1989 -
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References
Benzylbromide 8 was prepared from 5-iodo-salicylic acid in 40% overall yield as indicated in Scheme [6] .
9( S )-2-Amino-3-(2-benzyloxy-5-iodophenyl)propionic acid(11): Colourless crystals, mp 228-230 °C (decomp.). [α]D 20 = -11.8 (c 0.11, MeOH); 1H NMR (500 MHz, CD3OD): δ = 2.89 (dd, J = 9.2/14.3 Hz, 1 H, CH 2CH), 3.41 (dd, J = 4.7/14.3 Hz, 1 H, CH 2CH), 3.89 (dd, J = 4.7/9.2 Hz, 1 H, CH2CH), 5.18 (s, 2 H, OCH2), 6.86 (d, J = 8.6 Hz, 1 H, Harom), 7.28-7.49 (m, 5 H, Harom), 7.54 (dd, J = 2.2/8.6 Hz, 1 H, Harom), 7.57 (d, J = 2.2 Hz, 1 H, Harom); 13C NMR (125 MHz, CD3OD): δ = 33.5, 56.2, 71.3, 83.9, 115.9, 128.7, 128.9, 129.2, 129.8, 138.2, 138.8, 141.0, 158.3, 173.6; MS (MALDI): m/z = 398 [M + 1]. HRMS (CI, CH5 +): Anal. Calcd for C16H16NO3I (M + H+): 398.0253; Found: 398.0253.
18In addition to 20, 21 and 22 small amounts of the respective aryl iodide homocoupling product i (1-7%) and in case of entries 1-4 product ii (3-6%), which arises from aryl transfer by the arsine, were also obtained (Figure [2] ).
21Stille coupling of 5b and 6: A solution of 5b (29.5
mg, 37 mol) in degassed NMP (0.14 mL) was added to a stirred mixture
of anhydrous LiCl (4.3 mg, 102 mol), 6 (20.0
mg, 34 mol) and 23 (1.6 mg, 1.7 mol) in
degassed NMP (0.2 mL) at room temperature. The reaction mixture
was heated at 90 °C for 14 h. After cooling to room temperature,
the reaction mixture was diluted with CH2Cl2 and
filtered through a pad of silica gel. The filtrate was washed with
aqueous 1.3 M phosphate buffer pH 7.0 and water, dried (MgSO4)
and concentrated under reduced pressure. The resulting residue was
purified by prep. HPLC (LiChrosorb® Si 60 5 µm, n-heptane-EtOAc, 85:15) to give
20.9 mg (64%) 3 as a colourless
solid.
3: [α]D
20 = +10.3
(c = 0.95, CHCl3);
lit.
[5a]
: [α]D = +11.2. 1H NMR
(500 MHz, CDCl3) δ = -0.03 [s,
9 H, Si(CH3)3], 0.85-0.91
(m, 2 H, CH2CH
2Si),
1.35 [s, 9 H, C(CH3)3],
3.06-3.14 (m, 2 H, CHCH
2),
3.18-3.26 (m, 2 H, CHCH
2),
4.05-4.21 (m, 2 H, CH
2CH2Si),
4.56-4.67 (m, 2 H, CHCH2),
4.95-5.17 (m, 8 H, OCH2Ph), 5.38 (d, 1 H, J = 7.8 Hz, NHBoc),
5.61 (d, 1 H, J = 7.7 Hz, NHZ), 6.91 (d, 1 H, J = 8.6
Hz, Harom), 6.94 (d, 1 H, J = 8.6
Hz, Harom), 7.19-7.38 (m, 20 H, Harom.), 7.42-7.48
(m, 4 H, Harom).