Aldehydes functionalized, stereochemical course

Through extensive screening of compounds, " " " it was revealed that this enzyme accepts a very wide range of substrates. In addition to phosphorylated aldose, which are the native substrate, non-phosphorylated aldose, simple aliphatic, aromatic, heterocyclic and functionalized aldehydes, even with an increased hydropho-bicity, work as substrates. The stereochemical course has been elucidated in Fig. 18. The hydroxyl group on the 2-position of the aldehyde is very important and 2-deoxygenated aldehydes were rather weak substrates. The substrates with d-configuration at the 2-position have a stronger affinity to TKase than L-form. 

Transformation of the 7-oxo-2-enimides 28, available from chiral syn-aldols by a Cope rearrangement, into enantiopure tetrahydropyrans involves reduction of the aldehyde function followed by a fast intramolecular oxa Michael addition. The stereochemical course of the... 

A variety of aldehydes can function as heteroallenophiles in this [3 + 2] annelation (Figure 13 and Table 9). Reactions of the C(3)-substituted allenylsilanes (66) gave predominantly the ds-substituted dihydrofurans (71). The cis stereochemistry was anticipated, based on the well-documented stereochemical course of Lewis acid catalyzed additions of 3-substituted allylsilanes to aldehydes. ... 

As shown in the case of cinnamaldehyde, addition to the carbonyl functionality occurs in preference to attack at the electron-poor double bond. The extent to which stereogenic aldehydes can control the stereochemical course of these cycloadditions is discussed in Section 1.6.1.2.3.2. The success of the tin-based cocatalyst to induce reaction is explained in terms of the formation of an intermediate stannyl ether which exhibits greater reactivity towards 7t-allyl palladium cations than free alkoxide ions. The addition to ketones is less general and one of the more successful examples is given. 

Table IV. Stereochemical Course of 1,2-Additions Involving Bromo Esters and Functionalized Aldehydes.

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