Synthese des substances de groupe sanguin—IX

Directed and Efficient Syntheses of β(1→4)-Linked Galacto-Oligosaccharides

“…Only the pivaloylated donors 36 and 37 proved free of orthoester formation, yielding disaccharides 40؊42 efficiently (cf. Table 1) to satisfactory yields (48,64, and 70%), the 3,6-bis-allylated acceptor performing best here too (Table 1). Preparatively useful results were also obtained with the phenylsulfoxido galactoside 37, [59] which reacted with acceptors 27 and 31 through triflic anhydride activation under exceedingly mild conditions (1 h, Ϫ78 Ǟ 0°C) to yield the respective β(1Ǟ4)-disaccharides 41 and 42 in the 70Ϫ80% yield range.…”

“…The 3,6-di-O-benzylated allyl galactoside 23 was readily obtained from the easily accessible [48] benzylidene-galactoside 20 in a single three-step sequence: dibutyltin oxide-mediated benzylation proceeded with high regioselectivity to give the 3-O-benzyl ether 21, due to preferential reaction of the intermediate 2,3-O-stannylidene acetal at O-3; [ Ϫ Abbreviations used throughout: All ϭ allyl, Bn ϭ benzyl, Bz ϭ benzoyl, pMP ϭ p-methoxyphenyl, Ph ϭ phenyl, Piv ϭ pivaloyl subsequent benzoylation (Ǟ 22) followed by reductive fission of the 4,6-O-benzylidene ring with NaBH 3 CN/HCl [51] gave the suitably blocked model acceptor 23 in an overall yield of 78% for the three steps.…”

“…A suspension of allyl 4,6-O-benzylidene-β--galactopyranoside 20 [48] (8.02 g, 26 mmol) and Bu 2 SnO (6.47 g, 26 mmol) in toluene (250 mL) was refluxed for 16 h with azeotropic removal of water. After reduction of the volume to approximately 20 mL, benzyl bromide (9.7 mL, 82 mmol) was added, and the mixture was stirred at 90°C for 8 h. After concentration to dryness in vacuo, the residue was purified by elution from a silica gel column (eluent: toluene/EtOAc, 5:2) to give 9.…”

Mass spectrometry of middle molecules

“…The spectrum in Figure 2 is of negative ion clusters of isopropyl alcohol analyzed by a specially designed quadrupole system (1J); it illustrates the high mass transmission and limited resolution of this analyzer. Unit resolution through a mass range of about 1500 is now available on commercial quadrupole systems (12).…”

Synthesis of blood-group substances. Part 11. Synthesis of the trisaccharide O-α-D-galactopyranosyl-(1 → 3)-O-β-D-galactopyranosyl-(1 → 4)-2-acetamido-2-deoxy-D-glucopyranose

“…O-u-u-Galactopyranosy l-( 1-+3) -0-P-D-galactofJyranosyl-( 1+4) -2-acetamido-2-deoxy-~-glucopy~anose ( 17) .-Compound (15) (130 mg) in acetic acid (8 ml) was hydrogenolysed with Pd-C (lo?/, 100 mg) for 24 h. The mixture was filtered and evaporated to give the trisaccharide (17) (47 mg, 96y0), m.p. 236-239 "C (decomp.)…”