Synthesis ofD-Trigalacturonic Acid Methylglycoside and Conformational Comparison with Its Sulfur Analogue

Synthesis and Structural Characteristics of all Mono- and Difluorinated 4,6-Dideoxy-d-xylo-hexopyranoses

“…As shown in Scheme , Lindhorst et al successfully deoxyfluorinated the 1,2,3-tribenzoylated l -fucoside 22 . However, the high cost of d -fucose prevented us from using the same strategy, and a synthesis from methyl α- d -galactopyranoside 45 was carried out (Scheme ) which was converted to the known methyl 2,3-di- O -benzoyl-α- d -galactopyranoside 37 in three steps . Deoxygenation was envisioned via selective 6-bromination using an Appel reaction to give 66 .…”

“…Purification by chromatography ( Methyl 2,3-Di-O-benzoyl-4,6-dideoxy-4,6-difluoro-α-D-glucopyranoside (39). A suspension of 37 93 (8.90 g, 22.1 mmol) in CH 2 Cl 2 (10 mL) was cooled to −40 °C. DAST (25.5 mL, 193 mmol) was added, and the mixture was stirred for 24 h, over which time it was allowed to reach rt.…”

“…59 However, the high cost of D-fucose prevented us from using the same strategy, and a synthesis from methyl α-Dgalactopyranoside 45 was carried out (Scheme 7) which was converted to the known methyl 2,3-di-O-benzoyl-α-D-galactopyranoside 37 in three steps. 93 Deoxygenation was envisioned via selective 6-bromination using an Appel reaction to give 66. Adapting protocols from Cleóphax and co-workers, 94 1 equiv of CBr 4 was used to avoid any overhalogenation at OH-4.…”

Regiospecific Anomerisation of Acylated Glycosyl Azides and Benzoylated Disaccharides by Using TiCl4

“…Methyl 6‐ O ‐(2,3,4‐tri‐ O ‐benzoyl‐5‐ S ‐(methoxycarbonyl)‐α‐ L ‐arabinopyranosyl)‐2,3,4‐tri‐ O ‐benzoyl‐α‐ D ‐galactopyranose (39) : Regioselective glycosidation of 38 34, 35 (150 mg, 0.22 mmol) and 37 (100 mg, 0.22 mmol) as described above gave the intermediate alcohol (165 mg, 77 %) as a colorless foam; 1 H NMR (500 MHz, CDCl 3 ): δ =8.02–7.92 (m, 8 H; Ar‐H), 7.80 (d, 3 J (H,H)=7.3 Hz, 2 H; Ar‐H), 7.56 (t, 3 J (H,H)=7.5 Hz, 1 H; Ar‐H), 7.52–7.41 (m, 6 H; Ar‐H), 7.39–7.32 (m, 6 H; Ar‐H), 7.26 (dd, 3 J (H,H)=9.1, 6.5 Hz, 2 H; Ar‐H), 6.17 (d, 3 J (H,H)=3.3 Hz, 1 H; H‐4′ ′ ), 5.78 (dd, 3 J (H,H)=10.4, 7.9 Hz, 1 H; H‐2′), 5.69 (dd, 3 J (H,H)=10.7, 3.5 Hz, 1 H; H‐2), 5.62 (ddd, 3 J (H,H)=10.5, 7.3, 3.5 Hz, 2 H; H‐3 and H‐3′), 5.01 (d, 3 J (H,H)=3.5 Hz, 1 H; H‐1), 4.97 (d, 3 J (H,H)=7.9 Hz, 1 H; H‐1′), 4.61 (s, 1 H; H‐5′), 4.54 (s, 1 H; H‐4), 4.26 (dd, 2 J (H,H)=10.2 Hz, 3 J (H,H)=6.4 Hz, 1 H; H‐6a), 4.18 (t, 3 J (H,H)=6.3 Hz, 1 H; H‐5), 4.00 (dd, 2 J (H,H)=10.2 Hz, 3 J (H,H)=6.4 Hz, 1 H; H‐6b), 3.61 (s, 3 H; CH 3 ), 3.42(d, 3 J (H,H)=5.0 Hz, 1 H; OH), 3.17 ppm (s, 3 H; CH 3 ); 13 C NMR (125 MHz, CDCl 3 ): δ =166.8, 166.1, 165.8, 165.6, 165.2, 165.1 (each CO), 133.6, 133.4 (×2), 133.2, 133.1 (each CH), 130.0, 129.8 (×2), 129.7 (each CH), 129.5, 129.2, 128.8, 128.7 (each C), 128.6, 128.4 (2s), 128.3 (each CH), 101.4 (C‐1′ ′ ), 97.3 (C‐1), 72.6 (C‐5′), 71.3 (C‐3′), 70.9 (C‐2), 69.3 (C‐3 and C‐2′), 68.9 (C‐4′), 68.7 (C‐6), 68.5 (C‐5), 67.3 (C‐4), 55.1 (CH 3 ), 52.9 ppm (CH 3 ); ESI‐HRMS calcd for C 49 H 45 O 17 905.2657, found m/z (%) 905.2655 [ M +H] + . This intermediate (125 mg, 0.132 mmol) was benzoylated using pyridine (4 mL) and benzoyl chloride (30 μL, 0.263 mmol) as described above to give 39 (118 mg, 90 %) as a white solid after chromatography (petroleum ether/EtOAc 2:1); 1 H NMR (500 MHz, CDCl 3 ): δ =8.11–8.05 (m, 2 H; Ar‐H), 8.05– 8.00(m, 2 H; Ar‐H), 7.93 (m, 4 H; Ar‐H), 7.81–7.78 (m, 2 H; Ar‐H), 7.76–7.72 (m, 2 H; Ar‐H), 7.60 (m, 2 H; Ar‐H), 7.53–7.30 (m, 12 H; Ar‐H), 7.29–7.17 (m, 4 H; Ar‐H), 6.21–6.12 (m, 1 H; H‐4′), 5.90 (m, 2 H; H‐4, H‐3), 5.83 (dd, 3 J (H,H)=10.4, 7.9 Hz, 1 H; H‐2′), 5.61 (dd, 3 J (H,H)=10.4, 3.5 Hz, 1 H; H‐3′), 5.56 (dd, 3 J (H,H)=10.2, 3.6 Hz, 1 H; H‐2), 4.99 (d, 3 J (H,H)=3.6 Hz, 1 H; H‐1), 4.89 (d, 3 J (H,H)=7.9 Hz, 1 H; H‐1′), 4.58 (m, 1 H; H‐5′), 4.49 (m, 1 H; H‐5), 4.21 (dd, 2 J (H,H)=11.0 Hz, 3 J (H,H)=2.3 Hz, 1 H; H‐6a), 3.82 (dd, 2 J (H,H)=11.0 Hz, 3 J (H,H)=8.6 Hz, 1 H; H‐6b), 3.69 (s, 3 H; CH 3 ), 3.10 ppm (s, 3 H; CH 3 ); 13 C NMR (125 MHz, CDCl 3 ): δ =166.3, 166.1, 165.5 (2s) 165.3, 165.2 (2s) (each CO), 133.…”

Efficient Divergent Synthesis of New Immunostimulant 4″-Modified α-Galactosylceramide Analogues

“…PMB ethers, on the other hand, can be cleaved under mild and widely tolerated conditions, therefore permitting a broader substrate scope. 26 The previously reported trichloroacetimidate donor (13) 27 was synthesized via an improved scalable route from cheap -D-galactose pentaacetate (9) (Scheme 1). Introduction of the p-thiotolyl moiety as an anomeric protecting group and subsequent deacetylation under Zemplén conditions was followed by installation of the p-methoxybenzylidene acetal and protection of the remaining hydroxyl groups as PMB ethers to yield the fully protected intermediate 11.…”