Chemoenzymic preparation of asymmetrized tris(hydroxymethyl)methane (THYM*) and of asymmetrized bis(hydroxymethyl)acetaldehyde (BHYMA*) as new highly versatile chiral building blocks
作者:Giuseppe Guanti、Luca Banfi、Enrica Narisano
DOI:10.1021/jo00031a039
日期:1992.2
A series of asymmetrized tris(hydroxymethyl)methanes 2 and bis(hydroxymethyl)acetaldehydes 3 have been prepared in both enantiomeric forms through a chemoenzymatic methodology. The key step is the highly enantioselective PPL-catalyzed monohydrolysis of 2(E)-alkenyl-1,3-diacetoxypropanes 25-27. A careful study on the effect of unsaturations adjacent to the prochiral center in a series of 2-substituted 1,3-diacetoxypropanes has confirmed the suggested beneficial effect of a pi-system in that position but has also unveiled an unprecedented dramatic effect of double-bond configuration on enantioselectivity. A new empirical model for the interpretation of these and other results, based both on polarity and steric arguments, is proposed. This study provides a general protocol for the efficient synthesis of asymmetrized 1,3-propanediols bearing in position 2 saturated or unsaturated carbon chains.
Development of a Practical and Scalable Synthesis of (<i>R</i>)- and (<i>S</i>)-3-Amino-2-[(benzyloxy)methyl]propan-1-ol Monohydrochloride: A Useful C-4 Chiral Building Block
The development of a practical and scalable synthesis of a C-4 chiral amine building block (R)-1·HCl and (S)-1·HCl is described. This important chiral intermediate (R)-1·HCl is efficiently synthesized from the commercially available, inexpensive, and simple 2-(hydroxymethyl)-1,3-propanediol (31) using lipase-catalyzedenantioselective hydrolysis as a key reaction. Development resulted in a telescoped