Chemoenzymatic Synthesis of Optically Pure Planar Chiral (S)-(–)-5-Formyl-4-hydroxy[2.2]paracyclophane

Chiral isothiourea-catalyzed kinetic resolution of 4-hydroxy[2.2]paracyclophane

“…( R p )- 2a : Analytical data match those reported in literature [ 18 – 20 26 , 28 , 39 ]. TLC (heptanes/ethyl acetate 10:1; R f = 0.11).…”

“… a All reactions were carried out using 0.1 mmol rac - 2 and 0.06 mmol 4a in the presence of 0.06 mmol Hünig’s base (diisopropylethylamine, DIPEA) and 10 mol % ITU in the indicated solvent (0.11 M with respect to 2 ) unless otherwise stated; b determined by 1 H NMR of the crude product; isolated yields of 2 and 3 were almost quantitative in all cases; c determined by HPLC using a chiral stationary phase; d absolute configuration of recovered 2 was assigned to be ( R p ) by comparison of its (+)-optical rotation with previous reports [ 20 , 26 , 39 ]; e the s -factor was calculated from the ee of recovered 2 and/or the ee of ester 3 [ 40 – 43 ]; f using 5 mol % ITU 2 ; g using 1.1 equiv of 4a ; h isolated yield when carried out on 1 mmol rac - 2 scale. …”

Enantiopure planar chiral [2.2]paracyclophanes: Synthesis and applications in asymmetric organocatalysis

“…Among many other substrates, these biomolecules can catalyze the kinetic resolution of 4-acetoxy[2.2]paracyclophane (±)-37. [78][79][80] In the presence of commercially available Candida rugosa lipase (CRL) optically active 4-hydroxy[2.2]paracyclophane (R p )-16 has indeed been obtained in 47% yield and 96% ee through ester hydrolysis. Unreacted derivative (S p )-37 has been recovered as well in high yield and selectivity (Scheme 18).…”

Enzymatic approaches for the preparation of optically active non-centrochiral compounds

“…Similarly, Pietzsch and coworkers reported that the same enzyme efficiently resolved monoacetoxy-[2.2]paracylophane 94. 94,95 A crucial role was attributed to the cosolvent with diethyl ether allowing for enantioselectivities of k rel > 100 as opposed to e.g. toluene with k rel = 20.…”