Sulfoxide-mediated intramolecular

Sulfoxide-mediated intramolecular aglycone delivery has been conducted with a temporary linker formed in situ by the reaction of lanthanide triflates with the donor and acceptor-based alcohols (Scheme 4.66) [336], However, as the selectivities recorded were modest, it has to be assumed that intermolecular glycosylation was an important side reaction in this chemistry. 

Scheme 4.64 Sulfoxide-mediated intramolecular aglycone delivery.

Chloro-l,3-dimethylimidazolium chloride (DMC) [26] (R =R = Me, L = H in 11, Scheme 4.8a) not only acts as a powerful dehydration agent but also has unique and versatile abilities to chlorinate primary alcohols, to oxidize primary and secondary alcohols and to reduce sulfoxides and so on. In addition, DMC easily reacts with amines to yield the corresponding guanidines. Thus, methods of preparing monocyclic and bicyclic systems by application of DMC chemistry in the key steps have been developed [27] the reaction of DMC-type chloroamidine compounds with amines for trisubstituted mono-cyclic guanidines [27a] (Scheme 4.8a), the intramolecular cyclization of thiourea derivatives after activation with DMC for monosubstituted or disubstituted monocyclic and bicyclic guanidines [27b] (Scheme 4.8b), and the DMC mediated cyclization of... 

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