Further Studies on the Anti-Selective Aldol Reaction of Chiral Imides

Stenotrophomonas maltophilia OleC‐Catalyzed ATP‐Dependent Formation of Long‐Chain Z‐Olefins from 2‐Alkyl‐3‐hydroxyalkanoic Acids

“…To test our hypothesis on OleC, a series of various syn and anti enantiomeric pairs of 2‐alkyl‐3‐hydroxyalkanoic acids 4 a – c (Table ) and 3‐hydroxydecanoic acid were synthesized according to our reported procedures . Using Evans' aldol methodology, we also synthesized all four enantiomers of 2‐hexyl‐3‐hydroxydecanoic acid ((2 R ,3 S )‐ 4 a , (2 S ,3 S )‐ 4 a , (2 S ,3 R )‐ 4 a , and (2 R ,3 R )‐ 4 a ; Table ). The S. maltophilia oleC gene was expressed as a His 6 ‐tagged fusion protein in Escherichia coli and purified by affinity chromatography.…”

The Biochemical Basis for Stereochemical Control in Polyketide Biosynthesis

“…21a Syn -(2 S ,3 R )- 7a and (2 R ,3 S )-2-methyl-3-hydroxypentanoic acid ( 7b ) were each prepared by Evans asymmetric syn -selective aldol reaction followed by treatment with lithium hydroperoxide. 21b 30 .…”

“…21a Syn -(2 S ,3 R )- 7a and (2 R ,3 S )-2-methyl-3-hydroxypentanoic acid ( 7b ) were each prepared by Evans asymmetric syn -selective aldol reaction followed by treatment with lithium hydroperoxide. 21b 30 . (2 S ,3 R )- 7a and (2 R ,3 S )- 7b produced in high yield were each diastereomerically pure, as shown by 1 H NMR analysis, 27,31 and enantiomerically homogeneous as confirmed by optical rotation: [α] 25 D +4.1 ( c 2.1, Et 2 O) for (2 S ,3 R )- 7a and [α] 25 D −4.2 ( c 2.01, Et 2 O) for (2 R ,3 S ) 2-methyl-3-hydroxypentanoic acid ( 7b ).…”

“…(2 S ,3 R )- 7a and (2 R ,3 S )- 7b produced in high yield were each diastereomerically pure, as shown by 1 H NMR analysis, 27,31 and enantiomerically homogeneous as confirmed by optical rotation: [α] 25 D +4.1 ( c 2.1, Et 2 O) for (2 S ,3 R )- 7a and [α] 25 D −4.2 ( c 2.01, Et 2 O) for (2 R ,3 S ) 2-methyl-3-hydroxypentanoic acid ( 7b ). 21c The diastereomer (2 R ,3 R )- 8a was synthesized by the established stereoselective route 21d involving an asymmetric aldol reaction in which the use of 2 equiv. of Lewis acid n- Bu 2 BOTf favored the formation of the anti product over the syn .…”

Asymmetric processes

“…The N-propionyl Evans' oxazolidinone 8 reacts in an anti-manner with acetaldehyde (anti : syn = 7 : 1), where the only change from the standard Evans' conditions is the use of two equivalents of Bu 2 BOTf in the enolisation step. 8 A novel tartaric acid work-up is also described. The titanium enolate of propionate ester 9 gives good selectivities (anti : syn 85 : 15 to 99 : 1) with several aldehydes which have been precomplexed with TiCl 4 , but only a 44 : 55 dr with benzaldehyde.…”