Talopyranose

Draw structures for the products you would expect to obtain from reaction of /3-D-talopyranose with each of the following reagents ... 

Methyl p-D-talopyranose-2-C,4-C-diylphosphinite or 2-C,4-C-fmethoxyphosphanediyl)-p-D-glucopyranose or (2fl,4S)-2-C,4-C-(methoxyphosphanediyl)-P-D-/hreo-hexopyranose... 

The last then-unknown carba-sugar, carba-) -DL-talopyranose pentaacetate (83), was synthesized from 36 as follows. Epoxidation of 36 with sodium methoxide gave, at the early stage of the reaction, the 2,3-epoxide... 

CnH16C>7 Methyl 3,4-di-0-acetyl-2,6-anhydro-/ -D-talopyranose MATALP 38 442... 

An anhydro sugar which will probably find extensive synthetic use has been described by Hann and Hudson.85 This is the tricyclic compound, 3,4 1,6-dianhydro-jS-D-talopyranose (LXXIV) which is prepared by the saponification of the 4-tosyl derivative of mannosan (LXXIII). 

The authors also evidenced an increase of the percentages of a-talo-pyranose and a-ia/ofuranose upon 2H substitution at C(l) concomitantly with a decrease of the percentages of (l-conformers. This observed shift on the talopyranose anomeric equilibrium was attributed to the preference of the shorter C-2H bond (relative to the C l l bond) to assume an equatorial orientation. 

Ferner sind noch 2,3-0-Isopropyliden- und 3,4-0-Isopropyliden-l,6-anhydro-D-talopyranose bekannt 100,106,111)... 

Die Reduktion mit NaBH4 gibt im Falle der Verbindungen a, b imd c die entsprechenden Hydroxy-Derivate mit aquatorialer Konfiguxation (also Derivate der D-allo-, D-gulo- imd o-altro-Reihe), nur aus d" entsteht die 2,4-Di-0-p-toluolsulfonyl-l,6-anhydro-p-D-talopyranose mit axialer HydroxyIgruppe am C-3 32),... 

Femer wurde 1,6-2,3-Dianhydro-p-D-talopyranose durch alkalische Hydrolyse des Bariumsalzes des l,6-Anhydro-p-D-galactopyranose-2-sulfats gewonnen... 

Es wurde gefunden, dafi, wenn im Molekul eine axiale Hydroxyl-gruppe an C-3 vorhanden ist, nur diese oxydiert wird. So bildet sich bei der katalytischen Oxydation von l,6-Anhydro- 3-D-glucopyranose (750), 1,6-Anhydro-p-D-galaktopyranose (752), 1,6-Anhydro-p-D-mannopyra-nose (756) und 1,6-Anhydro-p-D-talopyranose (760) in guten Ausbeuten... 

Formation of l,2 5,6-di-0-isopropylidene-a-D-n7i( -hexo-furanos-3-ulose (Fig. 2.13, 2.4.2.1 Table 2.3) was one of the first carbohydrate oxidations effected by stoich. RuOyCCl [310, 311]. The reagent was also used for oxidation of 1,6-anhydro-3,4-0-isopropylidene-P-D-galactopyranose to the -P-D-/yxo-hexopyranos-2--ulose, part of a route leading to 1,6-anhydro-P-D-talopyranose (Fig. 2.15) [321]. 

Oxirane-ring opening of talopyranose (76) with (30 a) afforded a mixture of thiodisaccharides (77) and (78) in very good yield. Conventional treatment of (77) led to the allyl-2-thio-fucosyl-galactoside (79) (Scheme 23) [32]. 

Brimacombe and Tucker48 were able to prepare l,4-anhydro-6-deoxy-2,3-0-isopropylidene-/3-L-talopyranose by an uncomplicated ring-closure, with inversion, of 6-deoxy-2,3-0-isopropylidene-4-0-... 

Quite analogous ring-closures occur when the 1-O-acetyl derivatives of the rhamnopyranose and talopyranose derivatives are treated with sodium azide in N,N-dimethylformamide. l-O-Acetyl-6-deoxy-2,3-0-isopropylidene-4-0-mesyl-a-L-mannopyranose is converted exclusively into l,4-anhydro-6-deoxy-2,3-0-isopropylidene-/3-L-talo-pyranose. In this instance, the azide nucleophile attacks the l-O-ace-tyl group, liberating an 0-1 oxide ion which reacts with inversion of C-4. The 4-epimeric, l-O-acetyl-6-deoxy-talose derivative gives 60% of the direct inversion product l,4-anhydro-6-deoxy-2,3-0-isopropyli-dene-a-L-mannopyranose, together with other products.50... 

The deamination of methyl 3-amino-3-deoxy-/3-D-altropyranoside was studied in 1934, but the products were not fully characterized.14411 The syrupy product was converted into a methylated derivative that had an elemental analysis corresponding to that calculated for a methyl tetramethylhexoside. The conditions used for methyl-ation would have opened an epoxide ring. Methyl 2,3-anhydro-4,6-0-benzylidene-a-D-mannopyranoside precipitated quantitatively from solution when the corresponding 3-amino-3-deoxyaltroside derivative was deaminated in aqueous medium.145 Epoxide formation was likewise reported to be quantitative in the deamination of the analogous 2-amino-2-deoxyaltroside.83 145 On deamination, 4-amino-l,6-anhydro-4-deoxy-/3-D-mannopyranose also gave an epoxide, namely, 1,6 2,3-dianhydro-/3-D-talopyranose, in unspecified yield.146... 

Several nucleosides containing other sugar residues, such as arabinopyranose, arabino-furanose, mannopyranose, talopyranose, xylopyranose or xylofuranose, have been investigated by 13C NMR [676, 684]. The assignments of the signals of the carbohydrate moieties were mainly performed by comparison with the 13C resonances of the parent sugars. 

The first McCasland s pseudo-sugar, pseudo-a-DL-talopyranose (P) was synthesized from 4-acetoxy-2,3-dihydroxy-5-oxo-cyclohexanecarboxylic acid (6) as follows [13]. Reduction of the oxo acid 6 with sodium borohydride and subsequent esterification with methanol and trifluoroacetic acid, followed by acetylation gave methyl (1, 2, 3, 4/5)-2, 3, 4, 5-tetraacetoxycyclohexanecarboxylate (7). Hydrogenation of 7 with lithium aluminium hydride and successive acetylation yielded pseudo-a-DL-talopyranose pentaacetate (8). Hydrolysis of 8 in ethanolic hydrochloric acid gave pseudo-a-DL-talopyranose 9 in 23% overall yield from 6 [1] (Scheme 6). 

---