Sequence analysis of the sulfated rhamno-oligosaccharides derived from a sulfated rhamnan

► Three sulfated rhamno-oligosaccharides O1, O2 and O3 were prepared. ► The sequence of O1 was characterized by NMR spectroscopic analyses. ► The fragmentation pattern of O1 was recognized by ES-CID MS/MS. ► With the principles established, the sequences of O2 and O3 were deduced. ► ES-CID MS/MS is useful for sequence analysis of rhamno-oligosaccharides.