The Preparation and Biological Significance of Phytosphingosines
Howell, Amy R.
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Abstract: Phytosphingosines constitute a group of functionally related, long-chain aliphatic 2-amino-1,3,4-triols of which D-ribo-C18-phytosphingosine ((2S,3S,4R)-2- aminooctadecane-1,3,4-triol) is the most prevalent. D-ribo-Phytosphingosine is a bioactive lipid and is reported to be a potential heat stress signal in yeast cells. Phytosphingosines are widely distributed as structural components of sphingolipids in yeast, fungi, mammalian tissues and marine organisms. The long-chain base (phytosphingosine component) of the majority of the phytosphingolipids has 18-carbons; minor amounts of other chain lengths, especially C20, are also found, depending on their origin. Some of these phytosphingolipids exhibit important physiological activities. For example, there are a- and b-galactosyl- and glucosylphytoceramides that possess high tumor inhibitory potency. Due to the variety and significance of their biological activities and their scarcity in nature, phytosphingosines have become important synthetic targets. In general, approaches can be placed into three main categories. The first two rely on the chiral pool of amino acids and carbohydrates as the foundation for the asymmetric centers. Most amino acid strategies utilize (L)-serine. The carbohydrate-based approaches are the most abundant and employ a variety of common sugars and amino sugars. The third category of syntheses is based on asymmetric transformations. In this review the biological importance of phytosphingosines will be highlighted and approaches to their synthesis will be