New Effective Synthesis of (N-Acetyl- and N-Stearoyl-2-amino-2-deoxy-β-D-glucopyranosyl)-(1→4)-N-acetylnormuramoyl-L-2-aminobutanoyl-D-isoglutamine, Analogs of GMDP with Immunopotentiating Activity
Ethyl 3,4,6-tri- O -benzyl-2-deoxy-2-phthalimido-1-thio-β-D-glucopyranoside ( 5 ), prepared by benzylation of ethyl 2-deoxy-2-phthalimido-1-thio-β-D-glucopyranoside ( 4 ), was transformed by reaction with bromine into 3,4,6-tri- O -benzyl-2-deoxy-2-phthalimido-β-D-glucopyranosyl bromide ( 6 ). Thioglycoside 5 in the presence of methyl triflate and glycosylbromide 6 in the presence of silver triflate were used as glycosyl donors for condensation with benzyl 2-acetamido-3- O -allyl-6- O -benzyl-2-deoxy-α-D-glucopyranoside ( 7 ), to give benzyl 2-acetamido-3- O -allyl-6- O -benzyl-4- O -(3,4,6-tri- O -benzyl-2-deoxy-2-phthalimido-β-D-glucopyranosyl)-2-deoxy-α-D-glucopyranoside ( 8 ). Its reductive dephthaloylation with NaBH 4 /AcOH afforded benzyl 2-acetamido-3- O -allyl-4- O -(2-amino-3,4,6-tri- O -benzyl-2-deoxy-β-D-glucopyranosyl)- 6- O -benzyl-2-deoxy-α-D-glucopyranoside ( 11 ). Compound 11 was N -acylated to give benzyl 2-acetamido-4- O -(2-acylamino-3,4,6-tri- O -benzyl-2-deoxy-β-D-glucopyranosyl)-3- O -allyl-6- O -benzyl-2-deoxy-α-D-glucopyranosides ( 12a ) or ( 12b ). These compounds were converted into corresponding benzyl 2-acetamido-4- O -(2-acylamino-3,4,6-tri- O -benzyl-2-deoxy-β-D-glucopyranosyl)-6- O -benzyl-3- O -carboxymethyl-2-deoxy-α-D-glucopyranosides which, by condensation with H-L-Abu-D-isoGln(OBzl) followed by hydrogenolysis of protective benzyl groups, furnished glycopeptides 16a and 16b . Intramolecular O→N migration of the allyl protecting group followed by its reduction to the propyl residue by reaction of compound 8 with hydrazine or hydrazinium acetate, to give benzyl 2-acetamido-4- O -(3,4,6-tri- O -benzyl-2-deoxy-2-propylamino-β-D-glucopyranosyl)-6- O -benzyl-2-deoxy-α-D-glucopyranoside ( 9 ), is also described.