Glyceraldehyde Wittig reaction with

The first issue confronted by Myers was preparation of homochiral epoxide 7, the key intermediate needed for his intended nucleophilic addition reaction to enone 6. Its synthesis began with the addition of lithium trimethylsilylacetylide to (R)-glyceraldehyde acetonide (Scheme 8.6).8 This afforded a mixture of propargylic alcohols that underwent oxidation to alkynone 10 with pyridinium dichromate (PDC). A Wittig reaction next ensued to complete installation of the enediyne unit within 11. A 3 1 level of selectivity was observed in favour of the desired olefin isomer. After selective desilylation of the more labile trimethylsilyl group from the product mixture, deacetalation with IN HC1 in tetrahydrofuran (THF) enabled both alkene components to be separated, and compound 12 isolated pure. 

The only normal Wittig products [61 and 63 (R = OMe)] from the reaction of glyceraldehyde with acetyl- and (p-methoxybenzoyl)-methylenephospborane, respectively, were identified during these investigations [Refs. 7(a) and 7(f), respectively]. 

The second chirality source used in the synthesis of aminocyclopropane carboxylic acids was D-glyceraldehyde acetonide, which after Wittig-Homer-Emmons reaction provided the alkenes 61. Treatment with diazomethane and subsequent irradiation at low temperatures alforded the cyclopropanes 62, which were converted into several other derivatives by modification of the side chain (Scheme 11). Notably, the best results were obtained by irradiating in the presence of benzophenone as triplet sensitizer [33, 34]. Following a similar synthetic procedure allocoronamic acid 65 was prepared, which is one of the amino acids that can be processed by plant tissues and promises the possibility to control the enzymatic processes underlying plant growth and fruit ripening [35]. 

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... 

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