149402-16-4

Upstream product

• 73-34-7 6-deoxy-L-galactose 
• 24577-96-6 methyl 3,4-di-O-isopropylidene-α-L-fucopyranoside 
• 14687-15-1 methyl L-fucopyranoside 
• 58479-61-1 tert-butylchlorodiphenylsilane 
• 149402-15-3 Methyl-2-O-tert-butyldiphenylsilyl-3,4-O-isopropyliden-α-L-fucopyranosid 
• 488714-66-5 methyl 3-O-(tert-butyldiphenylsilyl)-α-L-fucopyranoside 

Downstream Products

• 488714-66-5 methyl 3-O-(tert-butyldiphenylsilyl)-α-L-fucopyranoside 
• 149402-19-7 Methyl-2-O-tert-butyldiphenylsilyl-3,4-dideoxy-α-L-3-enofucopyranosid 

Relevant academic research and scientific papers

Imidazole-promoted 1,4-migration of the tert-butyldiphenylsilyl group: Influence on the selectivity control of the silylation reactions of carbohydrate OH groups

The regioselective protection of secondary hydroxy groups of gluco-, galacto-, manno-, rhamno- and fucopyranosides using TBDPSCl with imidazole in DMF has been studied. It was found that the relative spatial arrangement of the OH groups modulates the silylation selectivity which arises from the combination of kinetic factors and the intramolecular migrations of the secondary TBDPS groups. The rearrangement of the TBDPS groups has a much larger effect on the α-D-manno- and α-L-rhamnopyranosides, allowing the protection of the OH groups at positions 2, 3 or 2 and 4, in synthetically useful yields, by changing the reaction conditions. The relative reactivity of the secondary OH groups seems particularly likely to be governed by steric factors. This trend provides a valuable approach to the synthesis of 3-O-tert-butyldiphenylsilyl-1-thio-β-L-fucopyranoside.

Total Synthesis of Isokalafungins and Isonanaomycins

The total synthesis of isokalafungins (2) and isonanaomycins (12), the first members of a nonnatural group of benzoisochromanquinone antibiotics hydroxylated only at C-6, is described.Pathway A (Scheme 1) yields the separated (+/-)-cis and -trans diastereomers of 2 and 12 and is especially suited for modifications of the dihydropyrane ring.On pathway B the chirality of C-1 is performed by using 3,4,6-trideoxy-α-L-glycero-hex-3-enopyranosid-2-ulose (22) as a main building block, for the first time synthesized from L-fucose (Scheme 2).According to Scheme 3, condensation of 22 with the intermediate 23 gives the new 6-hydroxylated variants (1S,3S,4S)-isonanaomycin D (30) and (1R,3R,4R)-isokalafungin (2).Pathway B favours modifications of the phenolic ring, which can strongly influence the spectrum of activity.Unexpectedly, the shifting of the hydroxy group from C-9 to C-6 changes the antibacterial properties unessentially. Key Words: Antibiotics, unnatural / Benzoisochromanquinones / Isokalafungins / Isonanaomycins