Efficient synthesis of pyruvic acetals of carbohydrate vicinal diols: 3,4-O-(1-methoxycarbonyl)ethylidene-d-galactopyranoside and 5,6-O-(1-methoxycarbonyl)ethylidene-d-galactofuranoside, via 1-hydroxy-2-propanone acetals
✍ Scribed by Kazumi Hiruma; Jun-ichi Tamura; Hironobu Hashimoto
- Publisher
- Elsevier Science
- Year
- 1996
- Tongue
- English
- Weight
- 654 KB
- Volume
- 282
- Category
- Article
- ISSN
- 0008-6215
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✦ Synopsis
Pyruvic acetals of carbohydrates are often found in bacterial lipopolysaccharides [I] and capsular polysaccharides [I], and also in glycolipids of fish nerve fibers [2]. In addition to tt~e most common 4,6-acetals of hexose residues [3,4], acetals of vicinal diols in the pyranose [5-8] and furanose [9] structures are known. Although several efficient methods h:we been reported for preparation of the 4,6-pyruvic acetals [10-16], the acetalation of vicinai diols has scarcely been examined [17]. We now report effective syntheses of 3,4-and 5,6-pyruvic acetals linked to methyl a-D-galactopyranoside and methyl /3-D-galactofuranoside, respectively, by a modification of the classical method using I-acetoxyo2-propanone as reported by Gorin and Ishikawa [18]. The novel coupling reaction of alkyl pyruvates with silylated diols in the presence of trimethylsilyl triflate (Me3SiOTf) [16] proved ineffective for preparation of these vicinai diols.