SN2′ Alkylation of Chiral Allylic CyanohydrinO-Phosphates with Organocuprates

Regio- and stereocontrol in the reactions of α-halo-β,γ-enoates and α-O-phosphono-β,γ-enenitriles with organocuprates

The reactions of (Z)- and (E)-ethyl 2-chloro-3-octenoate (4a and 17) and (E)- and (Z)-diethyl (1-cyano-2-heptenyl)phosphate (21a and 21b) with organocuprates were investigated as potential substrates for preparing γ-substituted α,β-enoates and enenitriles. In these copper-mediated allylic substitution reactions, the Z-isomer 4a displayed complete regio- and stereoselectivity (i.e., E:Z), while the regio- and stereoselectivity for E-isomer 17 varied as a function of solvent, cuprate reagent, transferable ligand, and cuprate counterion (e.g., Li(+) vs MgX(+)). Excellent selectivities could be achieved with 17 and (n)BuCuCNLi in Et2O. Conditions for improved selectivities in the reactions of allylic cyanophosphates over those previously reported were found. A series of relative rate and competition experiments was performed, and the degree of regio- and stereoselectivity for each system was rationalized in the light of the current mechanistic understanding of cuprate-mediated allylic substitution reactions.

Facile Synthesis of Clickable, Water-soluble and Degradable Polyphosphoesters

"Click" chemistry is a library of efficient and reliable reactions, which have been used to functionalize various classes of bio- and synthetic macromolecular systems for the incorporation of designed properties and functions. In this report, azide-alkyne Huisgen cycloaddition and thiol-yne reactions, two classical "click" chemistries, were employed to functionalize biodegradable, clickable polyphosphoester homopolymers and their water-soluble copolymers. A stable alkyne-functionalized phospholane monomer was synthesized, its organocatalyzed polymerization kinetics were evaluated, and the resulting (co)polymers were utilized to develop this facile method that provides the synthesis of clickable, water-soluble and degradable polyphosphoesters, which can be adapted for various applications.

α-Chloro-β,γ-ethylenic esters: enantiocontrolled synthesis and substitutions

Chiral nonracemic γ-seleno-α,β-ethylenic esters, when treated with sulfuryl chloride and ethyl vinyl ether in hexanes, produced α-chloro-β,γ-ethylenic esters in 65-75% yields, with ee values of 95-97%, and with 1,3-syn transfer of chirality. Reaction of these allylic chloride electrophiles with methylcuprate and with sodium azide nucleophiles afforded exclusively γ-substituted-α,β-ethylenic esters with faithful anti-transfer of chirality on multigram scale.

Bioreduction of alpha-methylcinnamaldehyde derivatives: chemo-enzymatic asymmetric synthesis of Lilial and Helional

Nonracemic aryl-substituted alpha-methyldihydrocinnamaldehyde derivatives employed as olfactory principles in perfumes (Lilial, Helional) were obtained via enzymatic reduction of the corresponding cinnamaldehyde precursors using cloned and overexpressed ene-reductases. (R)-Enantiomers were obtained using the old-yellow-enzyme (OYE) homolog YqjM from Bacillus subtilis and 12-oxophytodienoic acid reductase isoenzyme OPR1 from tomato (e.e.(max) 53%), and (S)-aldehydes were furnished in up to 97% e.e. using isoenzyme OPR3, nicotinamide 2-cyclohexene-1-one reductase NCR from Zymomonas mobilis and yeast OYE isoenzymes 1-3 under optimised reaction conditions in the presence of t-butyl methyl ether as the co-solvent. The stereochemical outcome of the reduction of alpha-methylcinnamaldehyde using NCR and OYEs 1-3 [previously reported to be (R)] was unambiguously corrected to be (S).