Readily prepared mannosyl n-pentenylorthoesters (NPOEs) serve as donors in themselves and as convenient intermediates for other glycosyl donors, such as n-pentenyl glycosides (NPGs), thioglycosides, and trichloroacetimidates. These various donors are activated by different reagents, and are therefore amenable to versatile, discriminate use. Scandium and ytterbium triflates respond very differently to these donors, with the result that chemoselective discrimination between NPOEs, NPGs, trichloroacetimidates as well as ethyl and phenyl thioglycosides can be achieved. Appropriate NPOEs are also able to provide 2,6 and 3,6 diol acceptors via rearrangement or glycoside formation, and these can be used for one-pot, sequential glycosidations based on orthogonal donors, and in situ double differential glycosidations. Thus NPOEs activated by iodonium ion, specifically generated from ytterbium triflate/N-iodosuccinimide, can be used to monoglycosidate the diols rapidly, with exquisite regio, and sometimes chemo, selectivity. The residual NPOE is converted into disarmed NPG, which is refractory to the reaction conditions, and so poses no threat to the free-OH of the monoglycosidation product. Further glycosidation of the latter can then achieved by direct addition of a trichloroacetimidate or ethyl thioglycoside. This basic strategy has been used to prepare a branched chain pentadecamannan. The success is an example of the efficiency of donor/acceptor MATCH concept for regioselective glycosylation.

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Lipomannan (LM) is one of the domains of lipoarabinomannan (LAM) glycolipids, the latter being one of several cell surface organic molecules that fortify mycobacterial species against external attack. Some members of mycobacterial families are pathogenic, most notably Mycobacterium tuberculosis and Mycobacterium leprae, while others are nonpathogenic, and used in the clinic, such as Mycobacterium smegmatis. Additional biological significance arises from the fact that LM has been implicated in several health disorders outside of those associated with mycobacterial pathogens, notably for treatment of bladder cancer. LM is comprised of a heavily lipidated phosphoinositide dimannoside headgroup, from which a mannan array, of varied complexity, extends. The latter consists of a 1,6-alpha-linked backbone flanked at position O2, not necessarily regularly, with alpha-linked mannosides. This paper gives an example of lipomannan synthesis in which all of the sugar components, whether functioning as donors or acceptors, are obtained from n-pentenyl orthoesters, themselves in turn prepared in three easy steps from D-mannose. Assembly of the mannan array is facilitated by the exquisite regioselectivity occasioned by the use of ytterbium triflate/N-iodosuccinimide as the trigger for reaction of n-pentenyl orthoesters.

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