Synthesis of two branched heptopyranoside‐ (L,D‐Hepp)‐containing trisaccharides of the inner‐core region of Citrobacter PCM 1487

The diastereogenic addition of (phenyldimethylsilyl)magnesium chloride to methyl 3‐O‐allyl‐2,4‐di‐O‐benzyl‐α‐D‐manno‐hexodialdo‐1,5‐pyranoside gave a L‐glycero‐D‐manno‐heptopyranoside (L,D‐Hepp) derivative having at C‐7 the phenyldimethylsilyl function as a hydroxy‐masking group. The L,D‐Hepp) derivative was converted into two acceptors which could be applied successfully for the preparation of the trisaccharides L‐α‐D‐Hepp)‐(1→3)‐O‐[L‐α‐D‐Hepp‐(1→7)]‐L‐α‐D‐Hepp/‐O‐Me 20 and α‐D‐Glcp‐(1→3)‐O‐[L‐α‐D‐Hepp‐(1→7)]‐L‐D‐Hepp‐O‐Me 26.