Tetrose derivatives

Other methods have been reported which, however, lacked generality. One of these described the approach to L-g/ycera-D-manno-heptopyranosides by stereoselective chain extension of suitably protected hexodialdo-l,5-pyranosides with silylmethylmagnesium chlorides [31]. Another method, quite reminiscent of the Masamune-Sharpless approach [7g], reported the synthesis of four stereoisomeric tetrose derivatives by homologation of... 

B. Achmatowicz, P. Raubo, and J. Wicha, Synthesis of four stereoisomeric tetrose derivatives... 

Question Two tetroses can be formed from L-glyceraldehyde. These tetroses are called l-erythrose and L-threose. Why is it unnecessary to invent new names for the tetroses derived from L-glyceraldehyde ... 

The nitroaldol condensation with nitromethane (Henry s reaction), followed by Nef decomposition of the resultant nitronate under strongly acidic conditions, has been used to elongate aldehydes. For instance, A-acetyl-D-mannosamine has been converted into A-acetylneuraminic acid applying this method iteratively [69]. Chikashita and coworkers [70] have reported good levels of anti diastereoselectivity better than 99% in an iterative homologation sequence using 2-lithio-l,3-dithiane [71] with 2,3-O-cyclohexylidene-D-glyceraldehyde R)-62. In the case of the BOM-protected tetrose derivative, the addition of 2-lithio-l,3-dithiane was syn selective (synlanti 82 18) (Scheme 13.30). 

The aldehyde l-149 reacts with diallylzinc to give 158 as the major product, the ozonolysis of which, when followed by acidic hydrolysis, furnishes 2-deoxy-L-fucose, which is a component of several antibiotics [103]. Similarly, 159 can be converted into L-mycarose (2,6-dideoxy-3-C-methyl-L-n7 (9-hexopyranose). The same anti preference is observed for all these diallylzinc additions (Scheme 13.56). Using allylmagnesium bromide leads to mixtures of anti and syn adducts. The syn adducts derived from l-149 and 159 were converted as above into 2,6-dideoxy-L-araZpmo-hexopyranose 160 and into L-boivinose 161, respectively. For other examples of tetrose derivative allylations, see Ref. [104]. 

SCHEME 13.116 Total asymmetric syntheses of tetritol and tetrose derivatives. 

Approaching to the synthesis of DAH [96], a suitable protected tetrose-derived 110 was coupled with 94 to afford the olefin 111. Conjugate... 

Isoxazolidinone 124 was synthesized from dehydroamino acid 123, which has a pentose sugar moiety at its side-chain, by displacement of the terminal mesylate by hydroxylamine with spontaneous cyclization by intramolecular Michael-like addition. Interestingly, when a tetrose-derived dehydroamino acid was substituted, no cyclization was observed. ... 

The influence of Li or Mg chelation on the regioselective azide ion-induced epoxide opening of 2,3-anhydro-tetrose derivatives is covered in Chapter 10, and azide ion opening of a l,6 3,4-dianhydrohexopyranose is detailed in Chapter 9. 

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