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382  17 Enzymatic Generation of Sialoconjugate Diversity

























             HO  OH                         HO  OH
                                   NeuA
                  O                              O    OH
            HO       O  OH     Pyruvate (5 equiv)  HO  O     OH
                 HO HO   O         85%           OH   HO   O   CO 2 H
                    HO      OH                         HO
                        46                  Galβ1,6Man  47  OH
                                                         OH
                                 Neu5Ac, CTP  α2,3SiaT  HO      CO 2 H
                                      CSS  89%
                                                       AcNH   O   O
                OH       HO  OH                   CSS     HO  OH  HO
            HO      HOOC
                             O     OH            α2,6SiaT            O    OH
                     O   O      O         OH                    O      O         OH
              AcNH                               Neu5Ac
                 HO  OH      OH   HO    O  CO 2 H  CTP    HOOC       OH   HO   O   CO 2 H
                               48   HO  OH        87%          O      49   HO  OH
                                                                 OH
                                                          HO    OH
                                                             HNAc
                                                          HO
            Scheme 17.17 Stepwise synthesis of an unusual tetrasaccharide (49) containing three sialic acid units around a galactoside core, by
            using sequential aldol and sialyltransfer reactions.
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