Protected glyceraldehyde

On the other hand, -chelation does not seem to play a role with the open-chained dibenzyl-protected glyceraldehyde 20 since there was no difference in the diastereoselcctivity of phenyl-lithium and phenylmagncsium bromide addition58. 

Trifluoromethylation of protected glyceraldehyde 8 is possible by slowly introducing trifluo-roiodomethane to a mixture of the aldehyde and zinc powder under irradiation with ultra sound, however, the diastereoselectivity of the addition reaction is low94. ... 

The dipolar cycloadditions of nitrone (—)-353 prepared from protected glyceraldehyde 347 (Scheme 74), to dipolar-ophiles 354, 356, and 358 afforded the heterocycles 355, 357, 359-361, respectively (Table 14) <2005JOC3157>. 

In 2002, the condensation of the titanium enolate derived from 2-pyridylthio acetoxyacetate with /V-4-methoxvphenvlimine of (S)-0,0-cyclohexylidene protected glyceraldehyde has been reported to give (35.4/C4 A)-p-lactam as a single product in 65% isolated yield (Scheme 52), [137]. A reactions sequence at C-3 and C-4 led in good yield to the p-lactam inhibitor of the serine protease prostate-specific antigen. 

To address limitations in the use of glyceraldehyde acetonide (43) as a three-carbon chiral building block, butane-2,3-diacetal-protected glyceraldehyde (44, R1 = R2 = H) has been prepared. It undergoes diastereoselective aldol reactions with a range of carbonyl compounds esters, thioesters, and ketones. The work has been extended (g) to other derivatives such as the a-substituted aldehyde (44, R1 = Me, allyl) and the methyl ketone (44, R2 = Me).122a,b... 

Access to the isomeric (L)-protected glyceraldehydes by this approach is limited because of the general unavailability of L-mannitol. One way of circumventing this problem is to employ a 2-step degradation of 5,6-0-isopropylidene-L-ascorbic acid 8 (scheme 4) (7). 

Scheme 1.10 Preparation of a amino acids from protected glyceraldehyde.

Additions to a,3-dialkoxy aldehydes (protected glyceraldehydes) are complicated by the possibility of chelation involving either the a or 3 alkoxy group. With 2,3-0-isopropylideneglyceraldehyde (62 equations 21 and 22) and Znh as catalyst, a preponderance of the 3-chelated complex (63) was obtained with consequent formation of the C-3,C-4 anti compounds as major isomers (Table 13, entries 1-3 Table 14,... 

Here the only product is the enantiomerically pure compound 8 (96%). The compounds 7 and 8 can be transformed into the corresponding Dispoke-protected glyceraldehydes 9, which not only are thermally more stable than the isopropylidene glycerinaldehyde, [2,7] but also have a distinctly higher anti-selectivity in the 1,2-addition of carbon nucleophiles to the aldehyde function [2] (Table 1). 

A reductive sequence of reactions has resulted in the synthesis of all four isomers of m-1,2-dihydroxypyrrolizidine (99) from the carbinol (98), formed from the combination of the oxygenated pyrrole (96) with the various isomers of the protected glyceraldehyde (97) (Scheme 26) <94JOC2906). 

Cydohexylidene-protected glyceraldehyde imines were used by Annunzi-ata et al. [54,55] for the synthesis of a 6-lactam precursor of thrombin and tryptase inhibitors [54], as well as for the inhibitor of serine protease [55]. 

Work has appeared describing the addition of allyltrimethyl-silane to the protected glyceraldehyde (9). This can be carried out under chelation- or non-chelation-controlled conditions, depending upon the choice of Lewis acid, leading to three contiguous oxygenated centres, two of which have defined stereo-64... 

Dihydroxyhexadiene 16 can be obtained by Wittig olefination of a protected glyceraldehyde and further deprotection. When reacted with acrolein (Scheme 5, Table 3), a strong solvent effect using water vs. toluene was observed (50 fold acceleration), a total endoselectivity, and an increase in the facial selectivity due to a differentiation of both faces of the diene with respect to hydrophobicity. This contrasted with the case of the reaction of glucosyl diene 2 which did not show any facial selectivity change with respect to solvent. For diene 16, the preferred attack by the... 

Additions to a,p-dialkoxyaldehydes (protected glyceraldehydes) are complicated by the presence of two alternative chelation pathways a or p chelation. With... 

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