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Synlett 2005(7): 1147-1151  
DOI: 10.1055/s-2005-865226
LETTER
© Georg Thieme Verlag Stuttgart · New York

Synthesis of the Phosphono Analogue of the Dimeric Subunit of Neisseria ­meningitidis Type A Capsular Polysaccharide

M. Isabel Torres-Sánchez, Veronica Draghetti, Luigi Panza, Luigi Lay*, Giovanni Russo
Dipartimento di Chimica Organica e Industriale and Centro Interdisciplinare Studi Bio-molecolari e Applicazioni Industriali (CISI), Università degli Studi di Milano, via Venezian 21, 20133 Milano, Italy
Fax: +39(0250)314061; e-Mail: luigi.lay@unimi.it;
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Publication History

Received 7 February 2005
Publication Date:
14 April 2005 (online)

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Abstract

The development of a glycoconjugate vaccine against N. meningitidis type A bacterium is greatly hampered by the chemical lability of the phosphodiester bridges joining the N-acetyl ­mannosamine repeating units of its capsular polysaccharide. We ­describe the first synthesis of the phosphonodisaccharide α-d-ManpNAc-[1→CH2-P(O)(O-)→6]-β-d-ManpNAc-(1→O) (CH2)3NH2 as a stable analogue of the corresponding phosphate-bridged disaccharide. The key phosphonoester linkage is obtained by condensation of monosaccharide building blocks under Mitsunobu conditions. Moreover, the protected precursor of the target compound is suitably designed to allow further elongation and synthesis of higher oligomers.

Key words

carbohydrates - Mitsunobu reaction - phosphonates - protecting groups - glycoconjugate vaccines

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All new compounds gave satisfactory analytical and spectroscopic data.

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Spectroscopic and analytical data of compound 11: [α]D 25 +20.7 (c 1.0, CHCl3). 1H NMR (400 MHz, CDCl3): δ = 7.37-7.19 (m, 15 H, Ph), 5.87 (d, 1 H, J = 9.3 Hz, NH), 4.65, 4.56 (each d, each 1 H, J gem = 11.7 Hz, CH 2 Ph), 4.55, 4.51 (each d, each 1 H, J gem = 11.9 Hz, CH 2 Ph), 4.46, 4.41 (each d, each 1 H, J gem = 11.5 Hz, CH 2 Ph), 4.36 (dt, 1 H, J 2,1 = 3.5 Hz = J 2,3, H-2), 4.16 (m, 1 H, H-1), 4.00 (dd, 1 H, J 5,6a = 5.1 = J 5,4, J 5,6b = 9.7 Hz, H-5), 3.82 (dd, 1 H, J 6a,6b = 10.0, H-6a), 3.78-3.69 (m, 3 H, H-3, H-4, H-6b), 3.74 (d, 3 H, J Me,P = 11.3 Hz, OMe), 3.71 (d, 3 H, J Me,P = 11.3 Hz, OMe), 2.13 (dt, 1 H, J 7a,1 = 9.3 Hz, J 7a,7b = 15.7 Hz = J 7a,P, H-7a), 2.04 (dt, 1 H, J 7b,1 = 4.0 Hz, J 7b,P = 15.7 Hz, H-7b), 1.87 (s, 3 H, COCH 3). 13C NMR (100.6 MHz, CDCl3): δ = 170.37 (CO), 138.39, 138.27, 137.74 (C ipso), 129.19-128.15 (Ph), 76.49 (C-3), 74.06 (C-5), 73.81, 73.35, 72.31 (3 CH 2 Ph), 72.31 (C-4), 68.79 (C-1), 68.69 (C-6), 53.26 (d, J OMe,P = 5.9 Hz, OMe), 52.60 (d, J OMe,P = 5.9 Hz, OMe), 45.28 (d, J 2,P = 14.8 Hz, C-2), 28.06 (d, J 7,P = 142.0 Hz, C-7), 23.71 (COCH3). 31P NMR (162 MHz, CDCl3): δ = 32.48. HRMS (MALDI): m/z calcd for C32H40NO8PNa: 620.2389 [M + Na+]; found: 620.2386; m/z calcd for C32H40NO8PK: 636.2129 [M + K+]; found: 636.2132.

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A fraction containing a single phosphorous diastereoisomer of 16 was isolated during column chromatography and fully characterized: [α]D 25 +8.1 (c 0.25, CHCl3). 1H NMR (500 MHz, CDCl3): δ = 8.25 (br s, 1 H, NH), 7.46-7.25 (m, 25 H, Ph), 5.76 (br d, 1 H, NH), 5.28 (br s, 1 H, NH), 5.11 (s, 2 H, CH 2 Ph Z), 4.95, 4.60 (each d, each 1 H, J gem = 10.7 Hz, CH 2 Ph), 4.89 (1 H, overlapping signal, H-2), 4.89, 4.51 (each d, each 1 H, J gem = 10.9 Hz, CH 2 Ph), 4.66, 4.59 (each d, each 1 H, J gem = 11.8 Hz, CH 2 Ph), 4.49, 4.42 (each d, each 1 H, J gem = 11.9 Hz, CH 2 Ph), 4.45 (br s, 1 H, H-1), 4.37-4.29 (m, 2 H, H-2′, H-6a), 4.22 (br dd, 1 H, J 6a,6b = 12.0 Hz, H-6b), 4.14 (m, 1 H, H-1′), 4.04 (dd, 1 H, J 3 ′ ,4 ′ = 9.7 Hz, J 3 ′ ,2 ′ = 5.4 Hz, H-3′), 3.92-3.77 (m, 6 H, H-4, H-7a, H-4′, H-5′, H-6′a, H-6′), 3.75 (d, 3 H, J Me,P = 10.9 Hz, OMe), 3.69 (dd, 1 H, J 3,4 = 8.3 Hz, J 3,2 = 3.7 Hz, H-3), 3.58 (m, 1 H, H-7b), 3.38 (br d, 1 H, J 5,4 = 9.5 Hz, H-5), 3.27 (m, 2 H, H-9a, H-9b), 2.23-2.06 (m, 2 H, H-7′a, H-7′b), 1.84 (br s, 6 H, COCH 3 ), 1.78 (m, 2 H, H-8a, H-8b). 13C NMR (125.7 MHz, CDCl3): δ = 171.62 (CO), 169.82 (CO), 156.52 (CO Z), 138.21 (2 × C), 137.92, 137.61, 137.11 (C ipso), 128.73-127.80 (Ph), 99.57 (C-1), 79.88 (C-3), 75.92, 73.01, 71.81 (C-4, C-4′, C-5′), 75.24, 73.35, 72.80, 71.06 (4 CH2Ph), 74.51 (C-5), 73.75 (C-3′), 68.24 (C-1′), 68.21 (C-6′), 67.49 (C-7), 66.79 (d, J 6,P = 38.5 Hz, C-6), 66.54 (CH2Ph Z), 53.87 (d, J OMe,P = 6.8 Hz, OMe), 49.94 (C-2), 48.68 (d, J 2 ′ ,P = 12.8, C-2′), 38.46 (C-9), 30.81 (C-7′), 29.64 (C-8), 23.98 (COCH3), 23.31 (COCH3). 31P NMR (202.5 MHz, CDCl3): δ = 29.71. HRMS (ESI): m/z calcd for C57H70N3O15PNa: 1090.4436 [M + Na+]; found: 1090.4410.

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Spectroscopic and analytical data of compound 17: [α]D 25 -40.5 (c 1.0, CHCl3). 1H NMR (400 MHz, CDCl3): δ = 7.78 (br s, 1 H, NH), 7.34-7.20 (m, 30 H, Ph), 5.92 (d, 1 H, J = 8.9 Hz, NH), 5.14 (s, 2 H, CH 2 Ph Z), 4.98, 4.62 (each d, each 1 H, J gem = 10.8 Hz, CH 2 Ph), 4.98, 4.52 (each d, each 1 H, J gem = 10.8 Hz, CH 2 Ph), 4.80 (br dd, 1 H, H-2), 4.74, 4.50 (each d, each 1 H, J gem = 11.3 Hz, CH 2 Ph), 4.63-4.52 (m, 3 H, H-1, H-2′, H-6a), 4.54, 4.47 (each d, each 1 H, J gem = 11.4 Hz, CH 2 Ph), 4.42, 4.32 (each d, each 1 H, J gem = 12.1 Hz, CH 2 Ph), 4.26 (m, 1 H, H-1′), 4.18 (br dd, 1 H, J 6a,6b = 11.4 Hz, H-6b), 3.98-3.87 (m, 3 H, H-4, H-5′, H-7a), 3.81-3.79 (m, 3 H, H-3′, H-4′, H-6′a), 3.73 (dd, 1 H, J 6 ′ b,6 ′ a = 9.7 Hz, J 6 ′ b,5 = 2.9 Hz, H-6′b), 3.68 (dd, 1 H, J 3,2 = 3.5 Hz, J 3,4 = 9.4 Hz, H-3), 3.53 (br s, 1 H, H-7b), 3.39 (d, 1 H, J 5,4 = 9.5 Hz, H-5), 3,34 (m, 1 H, H-9a), 3.10 (m, 1 H, H-9b), 2.27 (dt, 1 H, J 7 ′ a,1 ′ = 10.2 Hz, J 7 ′ a,7 ′ b = 16.8 Hz = J 7 ′ a,P, H-7′a), 2.07 (1 H, overlapping signal, H-7′b), 2.07 (s, 3 H, COCH 3 ), 1.85 (s, 3 H, COCH 3 ), 1.73 (m, 2 H, H-8a, H-8b). 13C NMR (100.6 MHz, CDCl3): δ = 171.79 (CO), 169.88 (CO), 159.46 (CO Z), 138.34 (2 × C), 138.11, 138.02, 137.87 (2, C ipso), 128.58-127.66 (Ph), 97.27 (C-1), 80.12 (C-3), 76.82 (C-3′), 75.38, 73.86, 73.30, 71.37, 70.74 (5 CH2Ph), 73.86 (C-5), 73.10 (C-4′), 72.74 (C-4, C-5′), 71.05 (C-1′), 68.40 (C-6′), 67.62 (CH2Ph Z), 65.13 (d, J 6,P = 37.8 Hz, C-6), 62.09 (C-7), 49.47 (C-2), 48.90 (d, J 2 ′ ,P = 15.3, C-2′), 37.40 (C-9), 28.76 (d, J 7 ′ ,P = 147.6 Hz, C-7′), 27.21 (C-8), 23.42 (COCH3), 22.94 (COCH3). 31P NMR (202.5 MHz, CDCl3): δ = 24.83. HRMS (MALDI): m/z calcd for C63H73N3O15PNa: 1166.4677 [M + H+]; found: 1167.4669; m/z calcd for C63H73N3O15PNa2: 1188.4575 [M + H + Na+]; found: 1189.4552.

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Spectroscopic and analytical data of compound 1: [α]D 25 -17.8 (c 1.0, H2O). 1H NMR (400 MHz, D2O): δ = 4.94 (d, 1 H, J 1,2 = 1.7 Hz, H-1), 4.69 (1 H, overlapped by HDO signal, H-2), 4.51 (br dd, 1 H, H-2′), 4.38-4.23 (m, 3 H, H-1′, H-6a, H-6b), 4.17-4.08 (m, 2 H, H-3′, H-7a), 4.02-3.93 (m, 4 H, H-3, H-7b, H-6′a, H-6′b), 3.81-3.73 (m, 3 H, H-4, H-4′, H-5′), 3.66 (m, 1 H, H-5), 3.26 (br t, 2 H, J = 7.5 Hz, H-9a, H-9b), 2.40-2.27 (m, 2 H, H-7′a, H-7′), 2.22 (s, 3 H, COCH 3 ), 2.20 (s, 3 H, COCH 3 ), 2.11 (m, 2 H, H-8a, H-8b). 13C NMR (100.6 MHz, D2O): δ = 175.73 (CO), 174.60 (CO), 99.73 (C-1), 75.63 (C-5), 74.44, 67.70, 66.90 (C-4, C-4′, C-5′), 72.84 (C-1′), 71.86 (C-3), 69.57 (C-3′), 67.97 (C-7), 63.38 (C-6), 60.77 (C-6′), 53.27 (C-2), 53.05 (d, J 2 ′ ,P = 9.7 Hz, C-2′), 38.02 (C-9), 27.80 (d, J 7 ′ ,P = 134.6 Hz, C-7′), 26.85 (C-8), 22.31 (2 COCH3). 31P NMR (162 MHz, D2O): δ = 22.95. HRMS (ESI): m/z calcd for C20H38N3O13PNa: 582.2034 [M + H+]; found: 582.2035; m/z calcd for C20H37N3O13PNa2: 604.1853 [M + Na+]; found: 604.1857.