In recent years, acyclic β-amino acids have attracted attention especially following their recogniti — Organic Chemistry Chemistry Question

In recent years, acyclic β-amino acids have attracted attention especially following their recognition as an important class of compounds in the design and synthesis of potential pharmaceutical drugs such as Taxol (paclitaxel) and its analogue Taxotere (docetaxel), currently considered to be among the most important drugs in cancer chemotherapy. The only source of Taxol is the bark of the pacific yew tree, Taxus brevifolia, but its Taxol content is relatively low. In efforts to overcome this supply problem, chemists have been working on semi-syntheses. These methods involve synthetic side-chain coupling to C^13-OH of the more readily available Baccatin III derivatives as given below, which can be isolated in higher yield from the needles of various Taxus species (e.g. Taxus baccata).

The racemic synthesis of side chain is started by refluxing benzaldehyde p-anisidine in toluene to afford compound A. Subsequent reaction of compound A with acetoxyacetyl chloride in the presence of triethylamine gives the racemic mixture of cyclic compounds B₁ and B₂ with the molecular formula (C₁₈H₁₇NO₄). The resultant racemic mixture of B₁ and B₂ is subjected to enzymatic resolution by using Lipase (Amano PS). Lipases are well known biocatalysts to hydrolyze the ester units. They selectively hydrolyze only one enantiomer of a racemic mixture. As a result of this hydrolysis, B₁ (as the unreacted enantiomer) and C (hydrolysis product) are isolated. B₁ has absolute configuration 3R,⁴S whereas, C has ³S,4R.