Sugar-derived aldehyde

The asymmetric Baylis-Hillman reaction of sugar-derived aldehydes as chiral electrophiles with an activated olefin in dioxane water (1 1) proceeded with 36-86% de and in good yields of the corresponding glycosides (Eq. 10.47).104 The use of chiral /V-mcthylprolinol as a chiral base catalyst for the Baylis-Hillman reaction of aromatic aldehydes with ethyl acrylate or methyl vinyl ketone gave the adducts in good yields with moderate-to-good enantioselectivities in l,4-dioxane water (1 1, vol/vol) under ambient conditions.105... 

The synthesis shown in Fig. 40 provided access to heptoses,55 but according to our definition, this is not a higher sugar synthesis. However, the approach to such derivative was based on the Baylis-Hillman reaction of acyclic sugar-derived aldehydes, a reaction not commonly applied in sugar chemistry and worth to mention in this review. 

The synthesis of oxazole C-nucleosides in moderate yields by Tosmic addition to sugar derived aldehydes and concomitant cyclization has been reported. In particular, aldehyde 130 gave 131 in 48% yield <03SL1619>. 

Condensation of L-cysteine with carbonyl compounds has been widely employed in the preparation of chiral thiazolidine 4-carboxylic acids <87JMC1891>. a-Hydroxyketenes <87JHC1629> or sugar-derived aldehydes <89CAR(187)223> have been used to form 2-(polyhydroxyalkyl)thiazohdines (Equation (73)) <94CAR(262)147>. This reaction has been also employed in peptide synthesis <94JA4149>. 

The examples presented in the previous two sections represent early approaches to the preparation of C-disaccharides. Building upon these early studies, new techniques became apparent and interesting reports surfaced in 1985. Aside from additional studies involving Diels-Alder methodology, Beau, et al.,7 reported the use of addition reactions between phenylsulfone anions and sugar-derived aldehydes as a viable method for the formation of C-disaccharides. As shown in Scheme 8.3.1, the sulfone associated with the addition product was cleaved on treatment with lithium naphthalide thus giving the final product. 

Later, Shaw and co-workers further employed sugar derived aldehydes 312 as electrophiles in the chalcogeno-MBH reaction (Scheme 2.170). The resulting allyl chlorides 313 can be easily transformed into allylamines 314 via treatment with various amine (Et2NH, pyrrolidine, piperidine and piperazine derivatives) (Scheme 2.170). They also evaluated these allyl chlorides and allylamines for their biological activity and found that (Z)-keto allyl chlorides possess antimycobacterial activity. ... 

Figure 7.8 Selection of sugar-derived aldehydes prepared by a quasi-Favorskii rearrangement-...

A similar reaction procedure with various sugar-derived aldehydes was published by Sapi et al. in 2010 [129]. Deprotection of the oxygen-substituents present in the aldehyde moiety led to the previously discussed decarboxylative cyclization in one additional step providing the desired products in good yields over two steps with high diastereoselectivity. 

E. Dardennes, S. Gerard, C. Petermann, J. Sapi, Tetrahedron Asymmetry 2010,21,208—215. Diasteieoseleetive trimoleeu-lar eondensation between indole, Meldrum s acid and chiral sugar-derived aldehydes. 

A new efficient and stereoselective synthesis of furo[2, 3 5,6]pyrano[4,3-i)]quinoline derivatives and has been achieved by intramolecular hetero Diels-Alder reactions of aldimines generated in situ from aromatic amines and the O-allyl derivative of the chiral sugar derived aldehyde in acetonitrile in the presence of a catalytic amount (10 mol%) of BiCl3. The products are formed with extremely high (>95%) trans-selectivity in good to excellent yields (Equation 20) [38a]. The authors have also carried out the diastereoselective synthesis of new hexahydropyrazolo[4, 3 5,6]thiopyrano[4,3-t>] in the similar conditions [38b]. 

The use of TDSOTf (or other acids such as BF3-OEt2, p-TsOH, ZnBr2, ZnCl2) as a catalyst to improve the addition of formaldehyde dialkylhydrazones to sugar-derived aldehydes resulted in undesired hydrazones formed via a direct and retro-[2 + 2]-cycloaddition process between the formaldehyde dialkylhydrazones and the sugar aldehyde. ... 

Diverse sugar-derived aldehydes 15 (Scheme 11.6) were used as chiral auxiliaries to perform the diastereoselective three-component Passerini reaction by reaction with p-toluenesulfonylmethyl isocyanide (17a, TosMIC) and carboxylic acids 16, giving... 

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