Synthesis of QS‐21‐Xylose: Establishment of the Immunopotentiating Activity of Synthetic QS‐21 Adjuvant with a Melanoma Vaccine

A helping hand: The adjuvant QS-21-xylose (see structure; the xylose residue is shown in red) was obtained in pure form by chemical synthesis. When combined with its synthetic apiose isomer to furnish synthetic QS-21 (sQS-21), the saponin combination was shown to aid the production of antibodies in mice when injected with a melanoma vaccine. The preparation of sQS-21 provides access to pure, functional saponin adjuvants of defined composition.