Studies directed toward the synthesis of carba-d-arabinofuranose

Formal total synthesis of Palmerolide A

“…20 Selective PMB protection for the allylic hydroxyl group present in 20 with p-methoxybenzyl bromide (PMB-Br) in presence of NaH furnished 21 in 91% yield with 5-7% bis-PMB protected product. 21 The remaining free alcohol 21 was masked as its MOM-ether 22 with methoxymethyl chloride (MOMCl) and N,N-diisopropylethylamine (DIPEA) in CH 2 Cl 2 . Having synthesized 6 and 7, the coupling of both the fragments was initially attempted under Yamaguchi conditions 8 which afforded the ester 23a in low yield with the mixed anhydride as the byproduct.…”

“…The crude product was purified by silica gel chromatography (EtOAc/hexane = 3:2) to afford the desired acid 6 (1. 21 24-5.14 (m, 2H), 4.36 (AB q , J = 12.1, 80.1 Hz, 2H), 3.77 (s, 3H), 3.69 (m, 1H), 2.3 (t, J = 6.8 Hz, 2H), 1.79-1.45 (m, 4H) ppm; 13 C NMR (75 MHz, CDCl 3 ) δ = 179. 5, 159.0, 138.5, 130.4, 129.3, 117.3, 113.7, 79.5, 69.6, 55.1, 34.6, 33.7, 20.5 …”

Carbasugar analogues of galactofuranosides: β-O-linked derivatives and towards β-S-linked derivatives

“…Related approaches to carbapentofuranose derivatives have been described before. [27][28][29][30][31][32][33][34][35] …”

First synthesis of 4a-carba-β-d-galactofuranose

“…9,10 As the C-4 stereochemistry is lost during the synthesis, it is possible to use the C-4 epimer of galactose, glucose, which is easily persuaded to adopt a furanose structure as its diacetonide derivative 2. To avoid the potential problem of selective protection of an allylic alcohol in the presence of another secondary alcohol, 10 we opted to use hemiacetal 3 as a key synthetic intermediate, so that the product of Grignard addition 4 would contain a 1,2-diol that could be selectively protected leaving 11 as the only free hydroxyl group.…”