Coupling of 6 with 8a to give 4,6-Di-O-acetyl-2-amino-2-N,3-O-carbonyl-2-deoxy-α-Dglucopyranosyl-(1 3)-1,2:5,6-di-O-isopropylidene-α-D-glucofuranose.

Transcription

1 General Experimental Procedures. NMR experiments were conducted on a Varian Unity/Inova 400-MHz Fourier Transform NMR Spectrometer. Chemical shifts are downfield from tetramethylsilane in CDCl 3 unless otherwise noted. Mass spectra were obtained on a Kratos MS-80 Mass Spectrometer (WSU Mass Spectrometry Facility). Analytical thin layer chromatography (TLC) was performed using silica gel 60 F254 precoated plates. Flash chromatography was performed using silica gel 60 ( mesh, EM science). High performance liquid chromatography was performed using a Waters delta Prep 3000 pump and gradient controller equipped with a Waters 2487 variable wavelength UV detector. All reactions were carried out under anhydrous, inert, atmosphere (nitrogen or argon) with dry, freshly distilled, solvents unless otherwise noted. Phenyl 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-1-thio-β-D-glucopyranoside 2. Thiophenol (6 ml, mmol, 1.2 eq) and SnCl 4 (4.21 ml, mmol, 0.7 eq) were added to a stirred solution of α-d-glucosamine pentaacetate 1 (20 g, mmol, 1 eq) in dichloromethane (100 ml). The reaction mixture was heated at reflux overnight, cooled to room temperature and quenched by addition of saturated aqueous NaHCO 3 (250 ml). The aqueous layer was separated and extracted with dichloromethane (3 75 ml). The combined organic layers were washed with brine, dried over Na 2 SO 4 and evaporated. The residue obtained was recrystallized in Et 2 O/Hexane (10/1) to give phenyl 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-1-thio-β-D-glucopyranoside 2 (22 g, 98%). Rf = 0.3 (3:2, Ethyl Acetate:Hexane); 1 H NMR (CDCl 3 ) δ 1.98, 2.01, 2.02, 2.07 (4s, 12H, 4CH 3 ); 3.71 (m, 1H, H-5), 4.03 (q, H-2), (m, 2H, 2H-6), 4.84 (d, 1H, J 1-2 = 10.2 Hz, H-1), 5.04, 5.20 (2t, 2H, H-3, H-4), 5.60 (s, 1H, NH), (m, 3H, ArH), (m, 2H, ArH). (See Buskas et al. (Tetrahedron Asymm. 5(11), , 1994) for characterization of this compound when prepared using different reagents). Phenyl 2-amino-2-deoxy-1-thio-β-D-glucopyranoside 4. To a stirred mixture of compound 2 (22 g, mmol, 1 eq) and DMAP (0.61 g, 5.01 mmol, 0.1 eq) in THF (150 ml) was added Boc 2 O (54.62 g, mmol, 5 eq). Stirring was continued at 60 C for 3 h at which time the reaction mixture was concentrated in vacuo and separated by flash chromatography (Toluene:Ethyl Acetate, 3:1) to give Phenyl 2-(N-tert-butyloxycarbonylacetamido)-2-deoxy- 3,4,6-tri-O-acetyl-1-thio-β-D-glucopyranoside 3 (26.50 g, 98%). Rf = 0.8 (3:2, Ethyl Acetate:Hexane); 1 H NMR (CDCl 3 )- N-diastereomeric mixture as shown. Mass Spec. (ESI) m/z (M + Na + ). Compound 3 (26.5 g, 49 mmol, 1 eq) in 100 ml methanol containing a catalytic amount of 1 M NaOMe solution was stirred for 1 h. The solvent was removed by evaporation to a volume of 20 ml, 5 ml TFA was added and the solution stirred for 24 hours at room

2 temperature. The reaction mixture was cooled with an ice bath, neutralized with 1M NaOH, then concentrated to dryness in vacuo. Purification using a short column of silica gel (EtOAc:MeOH:H 2 O, 7:2:1) gave free amine 4 (10.50 g, 80%) as a gum which solidified slowly. Rf = 0.4 (7:2:1, Ethyl Acetate:Methanol:H 2 O); 1 H NMR (D 2 O) δ 3.10 (t, J = 10.5 Hz, 1H, H-2), (m, 2H, H-4, H-5), 3.60 (t, 1H, H-3), 3.70 (dd, J = 15, 6.6 Hz, 1H, H-6), 3.8 (d, 1H, H- 6), 4.90 (d, J = 9.7 Hz, 1H, H-1), 7.30 (m, 3H, Ar-H), 7.50 (m, 2H, Ar-H). (See Buskas et al. (Tetrahedron Asymm. 5(11), , 1994) for characterization of this compound prepared using different methods). Phenyl 2-deoxy-1-thio-β-D-glucopyranosid[2,3-d]-1,3-oxazolidin-2-one 5. An ice-cooled solution of p-nitrophenoxycarbonyl chloride (19.50 g, mmol, 2.5 eq) in acetonitrile (50 ml) was added over several minutes to a stirred, ice bath-cooled, mixture of 4 (10.50 g, 38.7 mmol, 1 eq) and NaHCO 3 (16.25 g, 194 mmol, 5 eq) in 100 ml water. The mixture was vigorously stirred with ice-bath cooling for 1 hour after addition of the final aliquot of p-nitrophenoxycarbonyl chloride. The resulting aqueous mixture was extracted with ethyl acetate, the combined organic layers washed with water, dried over Na 2 SO 4, concentrated in vacuo and separated using a short column of silica gel (Ethyl Acetate) affording oxazolidinone 5 (9.20 g, 93%). Rf = 0.5 (Ethyl Acetate); 1 H NMR (CD 3 OD) δ 3.35 (t, J = 10.5 Hz, 1H, H-2), 3.50 (m, 1H, H-5), 3.72 (dd, J = 6.6, 5.7 Hz, 1H, H-6), (m, 2H, H-6, H-4), 4.17 (t, 1H, H-3), 4.91 (d, J = 9.7 Hz, 1H, H-1), (m, 3H, Ar-H), (m, 2H, Ar-H); Mass Spec. (ESI) m/z (M + Na + ). Phenyl 4,6-di-O-acetyl-2-deoxy-1-thio-β-D-glucopyranosid[2,3-d]-1,3-oxazolidin-2-one 6. A stirred solution of oxazolidinone 5 (9.20 g, 31 mmol, 1 eq) in Pyridine (50 ml) was treated with acetic anhydride (30 ml). After 6 hours the reaction was quenched with H 2 O (100 ml) and extracted with CH 2 Cl 2 (5 x 50 ml). The combined organic phases were dried (Na 2 SO 4 ), filtered and concentrated in vacuo. The residue was crystallized (CH 2 Cl 2 :Et 2 O,1:10) to give 6 (10.62 g, 90%). Rf = 0.4 (1:1, Ethyl Acetate:Hexane); 1 H NMR (CDCl 3 ) δ 2.14 (s, 6H, 2CH 3 ), 3.42 (t, 1H, H-2), 3.77 (m, 1H, H-5), (m, 3H, H-3, 2H-6), 4.73 (d, J 1-2 = 9.7 Hz, 1H, H-1), 5.22 (t, 1H, H-4), 5.8 (s, 1H, NH), 7.40 (m, 2H, Ar-H), 7.50 (m, 2H, Ar-H); Mass Spec. (ESI) m/z (M + Na + ). Phenyl 4,6-O-benzylidene-2-deoxy-1-thio-β-D-glucopyranosid[2,3-d]-1,3-oxazolidin-2- one 7. PhCH(OMe) 2 (9.45 g, 62 mmol, 2 eq) was added dropwise to a stirred solution of oxazolidinone 5 (9.20 g, 31 mmol, 1 eq) and camphorsulfonic acid (0.72 g, 3.10 mmol, 0.1 eq) in DMF (30 ml) at room temperature. The solution was then stirred at 60 C overnight, at which

3 time TLC showed complete disappearance of oxazolidinone 5. The reaction mixture was diluted with ethyl acetate (150 ml), extracted with saturated NaHCO 3 (75 ml) and brine (75 ml), dried over Na 2 SO 4, filtered and concentrated in vacuo. Purification by flash chromatography (Ethyl Acetate:Hexane, 2:3) afforded 7 (10.45 g, 90%). Rf = 0.5 (3:2, Ethyl Acetate:Hexane); 1 H NMR (CDCl 3 ) δ 3.45 (t, J = 9.7 Hz, 1H, H-2), 3.65 (m, 1H, H-5), 3.90 (t, J = 10.5 Hz, 1H), 4.00 (t, 1H), (m, 2H, H-6, H-6), 4.85 (d, J = 9.7 Hz, 1H, H-1), 5.60 (s, 1H, N-H), 5.70 (s, 1H, C-H), 7.40 (m, 6H, Ar-H), (m, 4H, Ar-H); Mass Spec. (ESI) m/z (M + Na + ). General Protocol for Glycosidation of 6. PhSCl (0.2 mmol, 2 equivalents) in dichloromethane (1 ml) was added slowly to a mixture of AgOTf (0.2 mmol, 2 equivalents) in dichloromethane (2 ml) at 78 C containing pulverized 3Å molecular sieves (20 mg). This mixture was stirred for 15 minutes, at which time, a solution of thioglycoside 6 (0.1 mmol, 1 equivalent) and DTBMP (0.2 mmol, 2 equivalents) in dichloromethane (2 ml) was added dropwise. After stirring this mixture for an additional 15 min., the acceptor alcohol (0.2 mmol, 2 equivalents) in dichloromethane (1 ml) was slowly added and stirring continued for 4 hours. The reaction was quenched by addition of saturated aqueous NaHCO 3 (1 ml), warmed to room temperature and diluted with dichloromethane (20 ml). The organic layer was separated, dried over Na 2 SO 4 and filtered. The resulting solution is treated with one equivalent of trimethylphosphine in dichloromethane (see note below), solvent removed in vacuo and product separated by flash chromatography. Note: The complete activation of oxazolidinone 6 requires at least 2 equivalents of PST because one equivalent is expended for N-sulfenylation of the oxazolidinone nitrogen. (Complete activation of donor is not observed if less than two full equivalents of PST are used.) Although TLC analysis during and after the reactions shows varied levels of the more non-polar N- phenylsulfenyl adduct, treatment of the completed reaction mixture with trimethylphosphine during work-up ensures quantitative removal of the sulfenyl group. Other thiophilic salts or agents will similarly facilitate removal of the phenylsulfenyl group adduct. The stability of the N- sulfenyl adduct varies with product and is not observed on TLC in some reactions. The addition of a thiophile to break the N-SPh adduct is not necessary in these later cases as quenching the reaction with sodium bicarbonate is sufficient for complete removal of phenylthio adduct from product. Coupling of 6 with 8a to give 4,6-Di-O-acetyl-2-amino-2-N,3-O-carbonyl-2-deoxy-α-Dglucopyranosyl-(1 3)-1,2:5,6-di-O-isopropylidene-α-D-glucofuranose. Rf = 0.3 (3:2, Ethyl Acetate:Hexane); 1 H NMR (CDCl 3 ) δ 1.30 (s, 3H, CH 3 ), 1.32 (s, 3H, CH 3 ), 1.40 (s, 3H, CH 3 ), 1.50 (s, 3H, CH 3 ), 2.10 (s, 3H, COCH 3 ), 2.15 (s, 3H, COCH 3 ), 3.70 (dd, J = 3.2 Hz, 1H, H-2),

4 3.95 (m, 1H, H-5), (m, 3H), (m, 4H), 4.55 (d, J = 4.0 Hz, 1H), 4.65 (t, 1H), 5.20 (s, 1H), 5.30 (d, J = 10.5 Hz, 1H), 5.33 (d, J = 3.2 Hz, 1H), 5.75 (d, J = 4 Hz, 1H); Mass Spec. (ESI) m/z (M + Na + ). Coupling of 6 with 8b to give Methyl (4,6-Di-O-acetyl-2-amino-2-N, 3-O-carbonyl-2- deoxy-α-d-glucopyranosyl)-(1 4)-3,6-di-O-benzyl-2-deoxy-2N-phthalimido-β-Dglucopyranoside Rf = 0.4 (2:1, Ethyl Acetate:Hexane); 1 H NMR (CDCl 3 ) δ 1.95 (s, 6H, 2 x CH 3 ), 3.01 (d, 1H), 3.25 (d, J = 9.7 Hz, 1H), 3.49 (s, 3H, CH 3 ), 3.51 (m, 1H), 3.55 (dd, 1H, H-2), 3.70 (q, J = 4.9 Hz, 1H), 3.80 (t, J = 8.9 Hz, 1H), 3.90 (t, J = 10.5 Hz, 1H), 4.35 (t, J = 9 Hz, 1H), (m, 2H), 4.70 (t, J = 9.7 Hz, 1H), 4.80 (s, 1H), 5.15 (t, J = 9.7 Hz, 1H), 5.27 (d, J = 9.7 Hz, 1H), 5.30 (m, 1H), 5.60 (s, 1H), (m, 5H, Ar-H), (m, 4H, Ar-H). Mass Spec. (ESI) m/z (M + Na + ). Coupling of 6 with 8c to give Methyl (4,6-Di-O-acetyl-2-amino-2-N, 3-O-carbonyl-2- deoxy-α-d-glucopyranosyl)-(1 6)-2-O-allyl-3,4-di-O-benzyl-α-D-mannopyranoside. Rf = 0.2 (1:1, Ethyl Acetate:Hexane); 1 H NMR (CDCl 3 ) δ 2.05 (s, 3H, CH 3 ), 2.10 (s, 3H, CH 3 ), 3.30 (s, 3H, OCH 3 ), (m, 2H), (m, 5H), (m, 4H), 4.40 (t, 1H), 4.45 (dd, J = 7.3, 5.7 Hz, 1H), 4.60 (d, J = <1 Hz, 1H), (m, 3H), 4.90 (d, J = 11.4 Hz, 1H), 5.25 (t, J = 4.9 Hz, 1H), 5.30 (d, J = 10.5 Hz, 1H), 5.50 (d, J = 3.2 Hz, H-1), (m, 2H), 6.40 (s, 1H), (m, 10H, Ar-H). Mass Spec. (ESI) m/z (M + Na + ). Coupling of 6 with 8d to give Methyl (4,6-Di-O-acetyl-2-amino-2-N, 3-O-carbonyl-2- deoxy-α-d-glucopyranosyl)-(1 3)-2-O-allyl-4,6-O-benzylidene-α-D-mannopyranoside. Rf = 0.3 (1:1, Ethyl Acetate:Hexane); 1 H NMR (CDCl 3 ) δ 2.08 (s, 3H, CH 3 ), 2.10 (s, 3H, CH 3 ), 3.40 (s, 3H, OCH 3 ), 3.60 (m, 1H), 3.70 (t, J = 1.6 Hz, 1H), 3.80 (dd, J = 4.1, 4.8 Hz, 1H), 3.90 (m, 1H), 3.95 (m, 1H), 4.10 (m, 1H), (m, 3H), (m, 3H), 4.65 (m, 1H), 4.75 (s, 1H), 4.90 (s, 1H), (m, 3H), 5.40 (d, J = 3.2 Hz, 1H, H-1), 5.60 (s, 1H), (m, 2H), (m, 5H, Ar-H); Mass Spec. (ESI) m/z (M + Na + ). Phenyl 2-amino-4,6-O-benzylidene-2-deoxy-1-thio-β-D-glucopyranoside 9. Sodium hydroxide (2 ml, 1M) was added to a stirred solution of oxazolidinone 6 (1g, 2.60 mmol, 1 eq) in THF (10 ml) at room temperature. The mixture was stirred for 3 hours, poured into H 2 O (100 ml) and extracted with ethyl acetate (3 x 50 ml). The combined organic phases were dried (Na 2 SO 4 ), filtered and concentrated in vacuo. The residue was crystallized from Et 2 O to give 9

5 (0.9 g, 95%). Rf = 0.3 (Ethyl Acetate); 1 H NMR (CDCl 3 ) δ 2.75 (t, 1H, H-2), 3.90 (m, 1H, OH), (m, 2H, H-4, H-5), 3.60 (t, 1H, H-3), 3.80 (t, 1H, H-6), 4.35 (dd, J = 4.8, 4.1 Hz, 1H, H- 6), 4.50 (d, J = 9.7 Hz, 1H, H-1), 5.50 (s, 1H, CH), (m, 3H, Ar-H), (m, 2H, Ar-H); Mass Spec. (ESI) m/z (M + Na + ). Phenyl 4,6-di-O-acetyl-2-deoxy-2-methoxycarbonylamino-1-thio-β-D-glucopyranoside 10. To a stirred solution of oxazolidinone 6 (1 g, 2.62 mmol, 1 eq) in methanol (10 ml) was added cesium carbonate (45 mg, 0.13 mmol, 0.05 eq). After stirring 3 hours at room temperature, the mixture was poured into H 2 O (100 ml) and extracted with Ethyl Acetate (3 x 30 ml). The combined organic phases were dried (Na 2 SO 4 ), filtered and concentrated in vacuo. The residue was crystallized from Et 2 O to give 10 (0.7 g, 80%). Rf = 0.7 (9:1, Ethyl Acetate:Methanol); 1 H NMR (CD 3 OD) δ 3.30 (m, 2H), 3.45 (m, 2H), 3.65 (m, 4H), 3.90 (m, 1H), 4.80 (m, 1H), 7.30 (m, 3H, Ar-H), 7.45 (m, 2H, Ar-H); Mass Spec. (ESI) m/z (M + Na + ). Phenyl 4,6-O-benzylidene-2-deoxy-2-trichloroethoxycarbonylamino-1-thio-β-Dglucopyranoside 11. To a stirred solution of oxazolidinone 7 (1g, 2.60 mmol, 1 eq) and trichloroethanol (7.80 g, 52 mmol) in THF (10 ml) was added cesium carbonate (45 mg, 0.13 mmol, 0.05 eq). The resulting mixture was stirred at room temperature for 3 hours, poured into H 2 O (100 ml) and extracted with ethyl acetate (3 x 30 ml). The combined organic phases were dried (Na 2 SO 4 ), filtered and concentrated in vacuo. The residue was crystallized from Et 2 O to give 11 (1.35 g, 95%). Rf = 0.8 (1:1, Ethyl Acetate:Hexane); 1 H NMR (CDCl 3 ) δ 2.90 (m, 1H, OH), (m, 2H, H-2, H-6), 3.60 (m, 1H, H-4), 4.10 (m, 1H, H-3), 4.40 (m, 1H, H-5), (d,d, 2H, CH 2 Cl 3 ), 4.95 (d, J = 9.7 Hz, 1H, H-1), 5.25 (m, 1H, N-H), 5.55 (s, 1H), (m, 10H, Ar-H); Mass Spec. (ESI) m/z (M + Na + ). Phenyl 2-amino-2-deoxy-1-thio-β-D-glucopyranoside 4. (via deprotection of 6) To a stirred solution of 6 (1 g, 2.62 mmol, 1 eq) in THF (20 ml) was added sodium hydroxide (2 ml, 1M) at room temperature. After 3 hours the solvent was removed in vacuo and purified using flash chromatography (ethyl acetate:methanol, 7:1) to give 4 (60 mg, 85%). (This material was identical in all aspects to that prepared by methods reported in scheme 1) Phenyl 6-O-benzyl-2-deoxy-1-thio-β-D-glucopyranosid[2,3-d]-1,3-oxazolidin-2-one 12. Hydrogen chloride in diethyl ether at room temperature was added to a mixture of 6 (1 g, 2.60 mmol, 1 eq) and sodium cyanoborohydride (2 g, 32.5 mmol, 12.5 eq) in 20 ml THF containing

6 3Å molecular sieves. The evolution of gas ceased after 5 min., at which time TLC indicated complete reaction. The mixture was diluted with CH 2 Cl 2 (100 ml) and water (20 ml) and separated. The organic phase was extracted with water (3 x 10 ml) and saturated aqueous NaHCO 3 (3 x 10 ml). The organic layer was dried over Na 2 SO 4, filtered and concentrated in vacuo. Purification by flash chromatography (Ethyl Acetate:Hexane, 1:1) afforded 12 (1g, 98%). Rf = 0.5 (1:2, Ethyl Acetate:Hexane); 1 H NMR (CDCl 3 ) δ 3.35 (m, 1H, H-2), 3.50 (s, 1H, OH), 3.60 (q, J = 4.1 Hz, 1H, H-5), 3.85 (m, J = 4.9 Hz, 2H, H-6), 4.01 (m, 1H, H-4), 4.15 (m, 1H, H- 3), 4.60 (m, 2H, CH 2 ), 4.70 (d, J = 9.7 Hz, 1H, H-1), 5.65 (s, 1H, NH), 7.27 (m, 8H, Ar-H), 7.50 (m, 2H, Ar-H); Mass Spec. (ESI) m/z (M + Na + ). Phenyl 4-O-acetyl-6-O-benzyl-2-deoxy-1-thio-β-D-galactopyranosid[2,3-d]-1,3- oxazolidin-2-one 13. Alcohol 12 (1g, 2.58 mmol, 1eq) dissolved in CH 2 Cl 2 (20 ml) was added to a stirred solution of trifluoromethanesulfonic anhydride (1.45 g, 5.16 mmol, 2 eq) and pyridine (0.21 ml, 2.58 mmol, 1 eq) in 10 ml anhydrous CH 2 Cl 2 at 25 C. After stirring at 25 C for 1 hour, the reaction mixture was poured into 200 ml ice water containing NaHCO 3 (2 g) and shaken vigorously. The aqueous layer was separated and extracted with CH 2 Cl 2 (3 x 30 ml). The combined organic extracts were dried over Na 2 SO 4, concentrated in vacuo and purified by flash chromatography providing the C4 triflate (1.12 g, 84%). Rf = 0.8 (1:1, Ethyl Acetate:Hexane); 1 H NMR (CDCl 3 ) δ 3.38 (m, 1H, H-2), 4.75 (m, 1H, H-5), 3.85 (m, 2H, H-6), 4.35 (m, 1H, H-3), 4.60 (m, 2H, CH 2 ), 4.70 (d, J = 9.7 Hz, 1H, H-1), 5.30 (m, 1H, H-4), 5.70 (s, 1H, NH), 7.27 (m, 2H, Ar-H), 7.40 (m, 8H, Ar-H), 7.60 (m, 2H, Ar-H); Mass Spec. (ESI) m/z (M + Na + ). Used immediately in next step. A mixture of triflate (1g, 1.92 mmol, 1eq) and sodium acetate (0.78 mg, 9.62 mmol, 5 eq) in DMF (20 ml) was stirred for 24 h at room temperature. The mixture was poured into ice water (15 ml) and extracted with ethyl acetate (3 x 20 ml). The organic layer was dried (Na 2 SO 4 ), filtered, concentrated in vacuo and purified by flash chromatography (Ethyl Acetate:Hexane, 2:1) to give 13 (0.75 g, 90%). Rf = 0.5 (1:1, Ethyl Acetate:Hexane); 1 H NMR (CDCl 3 ) δ 2, 01 (s, 3H, CH 3 ), 3.60 (m, J = 6.5 Hz, 2H, CH 2 ), 3.85 (m, 1H, H-2), 4,01 (m, 1H), 4.30 (dd, J = 2.4 Hz, 1H), 4.50 (AB, J AB = 12.1 Hz, 2H), 4.80 (d, J = 9.7 Hz, 1H, H-1), 5.10 (s, 1H), 5.60 (s, 1H), 7.30 (m, 8H, Ar-H), 7.50 (m, 2H, Ar-H). Mass Spec. (ESI) m/z (M + Na + ). Benzyl (2-Amino-2-deoxy-α-D-glucopyranosyl)-(1 4)-β-D-Glucopyranosiduronic acid 15. PhSCl (58 mg, 0.4 mmol) in dichloromethane (1mL) was added slowly to AgOTf (100 mg, 0.4 mmol) in dichloromethane (2 ml) at 78 C containing pulverized 3Å molecular sieves (20 mg). This mixture was stirred for 15 minutes, at which time a solution of thioglycoside 6 (76 mg, 0.2 mmol) and DTBMP (20 mg, 0.1 mmol) in dichloromethane (2 ml) was added dropwise. This

7 mixture was stirred at -78 C for 15 min followed by addition of the uronic acid acceptor alcohol (14) (50 mg, 0.1 mmol) in dichloromethane (1.5 ml). After stirring at 78 C for an additional 4 hours, the reaction was quenched by addition of saturated aqueous NaHCO 3 (2 ml), warmed to room temperature, diluted with dichloromethane (30 ml), separated and the organic layer dried over Na 2 SO 4. Concentration in vacuo followed by the addition of trimethylphoshine (1eq) and separation by flash chromatography (Ethyl Acetate:Hexane, 2:1) afforded protected disaccharide (60 mg, 75%). Rf = 0.5 (2:1, Ethyl Acetate:Hexane); 1 H NMR (CDCl 3 ) δ 2.10 (s, 6H, 2CH 3 ), 3.42 (dd, J = 8.9, 2.4 Hz, 1H, H-2), 3.70 (t, J = 2.4, 3.2, 1H), 3.85 (s, 3H, CO 2 CH 3 ), 4.20 (m, 2H), 4.50 (m, 2H), 4.65 (d, J = 12.1, 1H), 4.80 (m, 2H), 4.90 (d, 1H, J = 12.1 Hz, 1H), 5.18 (d, J = 3.2, 1H, H-1), 2.23 (t, 1H), 4.50 (m, 1H), 4.65 (t, J = 8.9 Hz, 1H), (m, 5H, Ar-H), 7.40 (m, 4H, Ar-H), 7.55 (m, 2H, Ar-H), (m, 4H, Ar-H). Mass Spec. (ESI) m/z (M + Na + ). Sodium hydroxide (1 ml, 1M) was added to a stirred solution of disaccharide, prepared as outlined above, (150 mg, 0.2 mmol, 1 eq) in THF (5 ml) at room temperature. The reaction mixture was stirred for 13 hours, cooled with an ice bath, neutralized with TFA and evaporated to dryness. Separation using HPLC afforded 15 (71 mg, 80%). Separation was performed using a mm, 10 µm particle size, Phenomenex Luna C18 semi-prep HPLC column. Mobile phase was composed of solution A (H 2 O, 0.1% TFA) and solution B (Acetonitrile, 0.1% TFA) with a linear gradient elution of; t=0.0 min [solution A (7.0 ml/min), solution B (0.0 ml/min)] to t=40 min [solution A (0.0 ml/min), solution B (7.0 ml/min)]; Ret. Time = 18.4 min. 1 H NMR (D 2 O/CD 3 OD) Significant aggregation was observed in single solvent systems due to detergentlike nature of this product, see 1-D and 2-D raw data appended; Mass Spec. (ESI) m/z (M + Na + ).