Enantioselective Kinetic Resolution of trans‐Cycloalkane‐1,2‐diols

Abstract

The kinetic resolution [1] of chiral trans-cycloalkane-1,2-diols (1) presents a formidable challenge [2] and a rare case where chemical methods are superior to enzymatic approaches. Taking the kinetic resolution of trans-cyclohexane-1,2-diol (1 a, n = 2) through monoacylation as the delineating test reaction, it was shown that various Pseudomonas lipases display both low activities (reaction times typically within the range of days) and low selectivities.[3] Purely chemical transformations utilizing benzoyl transfer in Cu II -catalyzed reactions with C 2 -symmetric bisoxazoline ligands give good ee values for the monobenzoylated product (around 80 %) and good conversions (37-46 %; selectivity factor s = 14-22) within hours; [4,5] Diol 1 a is resolved with up to 66 % ee.[4]

Oxidatively Induced Methyl Transfer from Boron to Platinum in Dimethyldi(2‐pyridyl)boratoplatinum Complexes

“…For the compartmentalization of the catalytic sites we chose a lipophilic admantane γ‐amino acid ( A Gly in our shorthand notation),10 which also enables the catalyst solubility in a broad variety of solvents. Such oligopeptides without apparent secondary structures11 have proven to be particularly effective in stereoselective acyl‐transfer reactions,5, 12 thus we have selected this type of catalyst for the present study.…”

“…As we already had a very active acylation platform at hand ( A , Scheme ),5, 12 we first focused our attention to attaching a terminal TEMPO moiety to the oligopeptide backbone (catalyst B , Scheme ). This represents a logical extension of acylation catalyst A and is a test of the degree of the required orthogonality of the reactivity of the individual CMs 5.…”

6.08 Acylation-Type Reactions: Synthesis of Esters via Acyl Transfer

“…In some rare examples, additional base is not required, because of the weakness of the generated acid (e.g., acetic acid). 27 Yet, the role of the base is not fully understood, because even in the latter case a rate acceleration is often observed, maybe because of assisting by the proton abstraction from the alcohol. 28 Additionally, the rate of the acylation is highly affected by the character of the anion and the solvent.…”

“…27,34 They did not try to form a stable β-hairpin structure by using L-proline/D-proline to generate secondary structure. This approach introduced a rigid and lipophilic nonnatural γ-adamantane amino acid as the structure forming building block in peptide catalyst 238.…”

Peptide‐Catalyzed Asymmetric Synthesis

“…They applied tetrapeptide 11 to the kinetic resolution of cyclic trans-1,2-diols [42] (Scheme 4.8). They applied tetrapeptide 11 to the kinetic resolution of cyclic trans-1,2-diols [42] (Scheme 4.8).…”