Dedicated to Professor Axel Zeeck on the occasion of his 65th birthday Saponins are natural products from plants and marine organisms exhibiting a wide variety of biological activities, for example, anticancer properties.[1] Most saponins consist of a lipophilic steroid or triterpene core and hydrophilic oligosaccharide side chains. Despite their structural diversity, only few saponins contain an additional monoterpene glycoside side chain (A, Scheme 1) like that found in julibrosides, [2] elliptosides [3] and avicins.[4] These compounds selectively inhibit tumor cell growth by induction of apoptosis [4a,c] (IC 50 : 0.2 mg mL À1 for Jurkat cells) and prevent chemically induced carcinogenesis in mice.[4d,e] The occurrence of the terpenoyl glycoside side chain A appears to enhance the cytotoxic effect, [2a] which encouraged us to develop a synthetic path to this unique motif for subsequent bioactivity studies.Our initial approach to terpenoyl glycosides was to functionalize linalool 1 with a carboxylate followed by glycosylation (Scheme 2). The tertiary alcohol function of racemic linalool (AE )-1 was acetylated, and the more substituted double bond was selectively cleaved to give the aldehyde 2 by epoxidation with MCPBA, periodic-acidcatalyzed diol formation, and oxidative cleavage of the vicinal diol.[5] The volatile aldehyde 2 was extended to furnish the desired menthiafolic acid ethyl ester 4[6] in a Horner-Wadsworth-Emmons (HWE) reaction [7] using phosphonate 3.However, the tertiary alcohol could not be deprotected without undesired side reactions. In the presence of base in methanol, the free hydroxy group participated in an intramolecular 1,4-addition, resulting in a mixture of eight possible diastereomers of the tetrahydrofuran derivative 5. In addition transesterification to the methyl ester and hydrolysis to the free acid were observed. In order to circumvent the use of a protective group for the OH function, the tertiary alcohol was glycosylated prior to

Professor Axel Zeeck zum 65. Geburtstag gewidmet Saponine sind Naturstoffe aus Pflanzen und marinen Organismen, die ein breites Spektrum biologischer Aktivitäten zeigen und z. B. gegen Krebserkrankungen wirksam sind. [1] Die meisten Saponine bestehen aus einem lipophilen Steroidoder Triterpengerüst und hydrophilen Oligosaccharid-Seitenketten. Die Strukturen der Saponine sind vielfältig, nur wenige aber enthalten eine zusätzliche MonoterpenglycosidSeitenkette (A, Schema 1), wie sie bei Julibrosiden, [2] Elliptosiden [3]

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