Preparation of (2 R , 3 R , 4 R )-3-hydroxy-2,4,6-trimethylheptanoic acid via enzymatic desymmertization

Stereoselective Synthesis of a Protected Side Chain of Callipeltin A

Matteson homologations of chiral boronic esters proved to be an excellent tool for the synthesis of highly functionalized amino and hydroxy acid residues. This method provides straightforward stereoselective access to the side chain of callipeltin A, a natural marine product with interesting biological activities. Furthermore, this protocol should allow for variations in the substitution pattern in future SAR studies, simply by choosing suitable nucleophiles during the homologation steps.

Scalable Syntheses and Biological Evaluation of Africane-type Sesquiterpenoids

Practical total syntheses of africane-type sesquiterpenoids were realized by reexamination of a divergent strategy employing optimized three-component coupling followed by ring-closing metathesis and substrate-controlled cyclopropanation. This sequential eight-step conversion provided Δ9(15)-africanene, a common bicyclo[5.3.0]decane intermediate for the syntheses of africane derivatives, in more than twice the yield as in the previous approach. The scalability and robustness of this improved synthetic route were confirmed by gram-scale preparation of Δ9(15)-africanene. In vitro cell-based assays of the synthesized africane-type sesquiterpenoids disclosed that ester-incorporating derivatives showed cytotoxic activity against HeLa cells. The effect of relative and absolute stereochemistry of africane-9,15-diol monoacetates on the cytotoxicity against HeLa cells was also investigated.

Synthesis of the cyclic heptapeptide core of callipeltin A

Macrolactonisation of a suitable heptapeptide precursor provides the cyclic depsipeptide core of callipeltin A in excellent yield.

Breaking Molecular Symmetry through Biocatalytic Reactions to Gain Access to Valuable Chiral Synthons

In this review the recent reports of biocatalytic reactions applied to the desymmetrization of meso-compounds or symmetric prochiral molecules are summarized. The survey of literature from 2015 up to date reveals that lipases are still the most used enzymes for this goal, due to their large substrate tolerance, stability in different reaction conditions and commercial availability. However, a growing interest is focused on the use of other purified enzymes or microbial whole cells to expand the portfolio of exploitable reactions and the molecular diversity of substrates to be transformed. Biocatalyzed desymmetrization is nowadays recognized as a reliable and efficient approach for the preparation of pharmaceuticals or natural bioactive compounds and many processes have been scaled up for multigram preparative purposes, also in continuous-flow conditions.

Asymmetric synthesis of (2S,3S)-3-Me-glutamine and (R)-allo-threonine derivatives proper for solid-phase peptide coupling

Practical new routes for preparation of (2S,3S)-3-Me-glutamine and (R)-allo-threonine derivatives, the key structural components of cytotoxic marine peptides callipeltin O and Q, suitable for the Fmoc-SPPS, were developed. (2S,3S)-Fmoc-3-Me-Gln(Xan)-OH was synthesized via Michael addition reactions of Ni (II) complex of chiral Gly-Schiff base; while Fmoc-(R)-allo-Thr-OH was prepared using chiral Ni (II) complex-assisted α-epimerization methodology, starting form (S)-Thr(tBu)-OH.