Total Synthesis of Trisaccharide Repeating Unit of O-Specific Polysaccharide of Pseudomonas fluorescens BIM B-582

Abstract

The first total synthesis of the trisaccharide repeating unit of the O-specific polysaccharide of Pseudomonas fluorescens BIM B-582 is reported. This efficient synthesis involves consecutive 1,2- cis glycosylations including β-l-rhamnosylation and α selective coupling of rare 4-deoxy-d- xylo-hexose as the key steps. The synthetic trisaccharide is equipped with an aminopropyl linker at the reducing end to allow for conjugation to proteins and microarrays for further immunological studies.

Recent progress in chemical synthesis of bacterial surface glycans

“…Synthetic targets chemically obtained include repeating units (RUs) and related oligomers or analogs of CPSs (1-25) [10,12,[19][20][21][22][23][24][25][26][46][47][48][49][50][51][52][53][54][55][56][57][58][59], LPSs and LOSs [28][29][30][31][32][33][34][35][36][37][60][61][62][63][64][65][66][67][68][69][70][71][72], cell wall polysaccharides (50)(51)(52)(53)…”

“…The LPS and LOS oligosaccharides and analogs obtained (Figure 2B) include those from B. pertussis (26) [60] ** ; P. aeruginosa STO11 (27) [61] ** ; P. shigelloide ST51 (28) [62]; B. cenocepacia (29) [28]; P. fluorescens BIM B-582 (30) [63]; H. pylori STO2 (31) [29] ** ; K. pneumoniae O2a (32) [30] ** ; P. chloroaphis UCM B-106 (33) [64]; S. boydii type type 18 (34) [65]; S. enteritidis (35) [31]; S. paratyphi A (36) [32] ** ; S. enterica O41 (37) [33], O51 (38) [66], O60 (39) [67]; E. coli O43 (40) [68], O75 (41) [69], O115 (42) [34], O156 (43) [70]; A. doebereinerae type strain GSF71 T (44) [71], P. alcalifaciens O22 (45) [78], rhizobial and agrobacterial LPS inner core (46) [72]; and C. jejuni LOS core (47) [35] ** ; Bradyrhizobium sp. BTAi1 (48) [36] ** and P. cryohalolentis K5 T (49) [37].…”

“…For example, a remote C3-O-picoloyl group in a rhamnosyl thioglycoside donor (F3A_1) was used to install the 1,2-cis-glycosyl linkage in the L-Rha-β1-4Glc disaccharide building block (F3A_3) of compound 3 [10] stereoselectively (53% yield with an α:β ratio of 1:3) by a hydrogen-bond-mediated aglycon delivery (HAD) strategy (Figure 3A). A similar strategy was used for synthesizing the L-Rha-β1-4GlcNAc disaccharide building block (F3A_6) of compound 30 with 80% yield and an α:β ratio of 1:8.4 [63]. L-Rha-β1-4-L-Rha and L-Rha-β1-4GlcNAc disaccharide units in compounds 34 [65] and 42 [34], respectively, were obtained similarly.…”

“…L-Rha-β1-4-L-Rha and L-Rha-β1-4GlcNAc disaccharide units in compounds 34 [65] and 42 [34], respectively, were obtained similarly. Another strategy is to synthesize a C2'-epimer of L-Rha-β1-4GlcNAc disaccharide building block (F3A_9) by an easier to control 1,2-trans-glycosylation of an Lquinovose donor (a C2-epimer of L-Rha building block) (F3A_7) followed by postglycosylational inversion of the C-2 of the L-quinovose in the disaccharide (F3A_8) [63]. Recently, 4-nitro-substitution of the picoloyl group in the rhamnosyl thioglycoside donor (F3A_10) was found to further improve its HAD effect for stereoselective formation (88% yield and an α:β ratio of 1:15) of L-Rha-β1-4Glc disaccharide building block (F3A_12) of compound 53 [76] ** .…”

Influence of Remote Picolinyl and Picoloyl Stereodirecting Groups for the Stereoselective Glycosylation

“…Kulkarni and coworkers in 2018 [45] reported the utility of C‐3‐ O ‐picoloyl protected L‐rhamnosyl donor for the total synthesis of the trisaccharide repeating unit of the O ‐specific polysaccharide from Pseudomonas fluorescens BIM B‐582 via picoloyl (HAD)‐mediated glycosylation for the synthesis of the key disaccharide 95 . For that, they coupled C‐3‐ O ‐picoloyl group in the L‐rhamnosyl donor 93 and 4‐OH glucosamine acceptor 94 under NIS/TfOH promotion conditions to obtain disaccharide 95 (α/β=1: 8.4) in 80% yield.…”