D-Rhamnal

When 3,4-di-O-benzyl-D-rhamnal is reacted with methyl a-D-evermicoside by the glycosyloxy-selenenylation procedure (phenylselenenyl chloride, acetonitrile,. vy/w-collidine, 1 h) 1, 2 -trans-diaxial (1-3) linked disaccharide 20 is obtained in 70% yield31. 

Another synthesis of D-oUvose derivative exploited a tungsten carbonyl catalyzed alkynyl alcohol cycloisomerization reaction [54,55]. This useful method allows for synthesis of variety of glycals from an achiral precursor (35), which after enantioselective reduction and Sharpless epoxidation afforded intermediates 39 and 42 (by Mitsunobu inversion), precursors of unnatural D-rhamnal (40) and valuable L-fucal (43) derivatives, respectively (Scheme 4). 

Anhydro-2,6-dideoxy-D-strabino-hex-l -enitol. D-Rhamnal. 6-Deoxy-D-glucal. 6-Deoxy-D-mannal [78086-61-0]... 

CioHmO 214.218 Syrup. Mg -76.4 (c, 0.28 in CHCI3). 3-Me 3-O-Methyl-D-rhamnal. 6-Deoxy-3-O-methyl-D-glucal C7H12O3 144.17... 

Iselin, B. et al, Helv. Chim. Acta, 1944, 27, 1200-1203 L-Fuccd, synth, L-Fucal di-Ac) Vischer, E. et al, Helv. Chim. Acta, 1944, 27, 1332-1345 (3-Methyl-D-rhamnal, 3-Methyl-D-rhamnal 4-Ac)... 

MethyIene-D-talitol, T-3 3-0-Methyl-D-rhamnal, D-679 3-0-Methyl-L-rhamnal, D-679 Narbosine E, H-76... 

The L-arabinose derivative 205 provides the starting point for synthesis of the 2-deoxythreose derivative 206, then converted to the acyclic nucleotide analogue 207 (which is twice as active against cytomegalovirus as its (5)-enantiomer). The chiron 208 has been synthesized starting from L-ascorlric acid, while diacetyl-D-rhamnal has been converted to 209 in six steps. The carbohydrate-derived meso epoxide diacetate 210 has been efficiently desymmetrized (to the monoacetate) using... 

Peracetylated D-glucal, D-galactal, and D-rhamnal were selectively deprotected at 04 by treatment with hydrazine acetate in DMF (see Vol.20, Chapter 13, ref.3). The possibility of initial deacetylation at the primary position followed by 4- 6 acetyl migration was excluded on the basis of experiments with deuteroacetylated starting compounds." The 4->6 acetyl migration to give the 3,6-diacetate (14) from its 3,4-isomer (13) has been studied in some detail and optimized in order to prepare (l->4)- and (l- 6)-linked disaccharides from a common carbohydrate aglycon (see Chapter 3). ... 

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