Among the large number of known tumor-associated carbohydrate motifs, Tn (GalNAca1!O-Ser/Thr) and sialylTn (Neu5Aca2!6GalNAca1!O-Ser/Thr) are the most specific to human epithelial tumor cells (breast, colon, ovarian, lung, and pancreatic cancers). [1] The sialylTn antigen, which is expressed on membrane-bound mucin-type glycoproteins, appears in transformed cells by premature sialylation of Nacetylgalactosamine, the first sugar moiety of the nascent Oglycane side chains in glycoproteins. [2] Integration of these antigens into synthetic vaccine constructs induces an anticancer immune response in which the carbohydrate domain plays a decisive role in determining immunogenicity. [1,3] The glycosylated antigen is, however, partially deglycosylated during the priming period. [4] It is therefore important to evaluate compounds in which the carbohydrate moiety cannot be detached from the peptide. We previously reported a mimic of the Tn antigen that could be incorporated into immunogenic glycopeptides. [5] We now describe the easy access to a carbon-linked mimic 2 of the Neu5Aca2! 6GalNAca1!OR disaccharidic component of the sialylTn antigen (Scheme 1). [6,7] Scheme 1. SialylTn tumor antigen 1 and a stable analogue of the sialyl-N-acetylgalactosaminyl donor 2 for "block" synthesis.