Allose 2-deoxy-2-fluoro

R. Ashique, R.V. Chirakal, D.W. Hughes, G.J. Schrobilgen, Two-step regio- and stereoselective syntheses of [F-19]- and [F-18]-2-deoxy-2-(R)-fluoro-beta-D-allose, Carbohyd. Res. 341 (2006) 457-466. 

R, = OH, Rj = H, R2 = OH, R4 = CHjOH in Table 3), the enantiomeric compound of the one just reported could be easily prepared. Aldol condensation products were obtained as diastereomeric mixtures from L-sugars, such as L-fucose, L-xylose, L-lyxose, and o-sugars epimeric to o-mannose relative to the 3-position, such as D-allose and o-gulose [46-48]. Table 4 lists the corresponding aldol condensation products isolated as diastereomeric mixtures. Also, 3-deoxy-D-mannose by condensation with pyruvate gave a diastereomeric mixture of 6-deoxy-KDN furanose derivatives [43]. All these results confirm that sialic acid aldolase, similar to other aldolases, exhibits broad specificity toward the electrophilic acceptor on the other hand, only pyruvate was reported acceptable as the donor [10]. But very recently, in contradiction to that, 3-fluoro-Neu5Ac and 3-fluoro-KDN could be prepared by the sialic acid aldolase-catalyzed condensation of 3-fluoropyruvate and Af-acetylmannosamine or o-mannose (Scheme 5) [47]. 

One year later, Kitazume et al. also described the synthesis of 6-deoxy-6,6,6-trifluoro-D-mannose and D-allose using intermediate (45,55)-76 (Scheme 5.10). Thus, oxidation of 76 with potassium permanganate in the presence of catalytic 18-crown-6 provided the diol 84 as the only isomer in 42% yield. Protection of diol moiety in 84 as its acetonide followed by DlBAL-H reduction afforded the lactol 85, which was subjected to the t-BuOK promoted isomerization to give the desired fluoro sugar 86 in 35% yield. The precursor 87 of fluoro sugar 89 was obtained by reduction... 

Tri-O-acetyl-D-glucal has been converted into 3,4,6-tri-0-acetyl-2-deoxy-2-fluoro-a-D-glucopyranosyl fluoride (35%) and the corresponding -o-manno-difluoride (26%) by reaction with fluorine diluted with argon at — 78°C. This method could be used to introduce a F-Iabel into 2-deoxy-2-fluoro-D-glucose, which is readily obtained by hydrolysis of the a-D- /uco-difluoride. The reactions shown in Scheme 26 have been used to synthesize 2-deoxy-2-fluoro-D-allose a... 

Primary and secondary hydroxyl groups can be fluorinated by reaction with di-ethylaminosulfiir trifluoride (DAST) [103]. The reaction of asymmetric secondary alcohols produces inversion of the configuration. Thus, the reaction of the protected diacetone allose with DAST, followed by removal of the protective groups, gives 3-deoxy-3-fluoro-D-glucose [104] (reaction 4.100). 

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