De novo protein design has been successful in expanding the natural protein repertoire. However, most de novo proteins lack biological function, presenting a major methodological challenge. In vaccinology, the induction of precise antibody responses remains a cornerstone for next-generation vaccines. Here, we present a protein design algorithm called TopoBuilder, with which we engineered epitope-focused immunogens displaying complex structural motifs. In both mice and nonhuman primates, cocktails of three de novo–designed immunogens induced robust neutralizing responses against the respiratory syncytial virus. Furthermore, the immunogens refocused preexisting antibody responses toward defined neutralization epitopes. Overall, our design approach opens the possibility of targeting specific epitopes for the development of vaccines and therapeutic antibodies and, more generally, will be applicable to the design of de novo proteins displaying complex functional motifs.

The asymmetric conjugate addition of dialkylzincs is usually performed with Cu(OTf)(2) in toluene. We show that by using a copper carboxylate in Et(2)O, THF, or EtOAc, we strongly improve the enantioselectivity with a given ligand. Ee values up to 99.1% could be reached with new ligands based on the induced atropisomerism of a simple biphenol unit. In addition, we show that the Lewis acid effect of Cu(OTf)(2) is not a significant.

Phosphoramidite ligands, based on a chiral amine and atropoisomerically flexible biphenols, induce high enantioselectivities (ee's up to 98%) in the copper-catalyzed conjugate addition of dialkyl zinc reagents to a variety of Michael acceptors.There have been many efforts in the field of asymmetric conjugate addition through copper-catalysis. 1 Among the various ways to introduce the chiral information, we demonstrated that trivalent phosphorous ligands were particularly efficient. 2 Later on, we introduced the use of diorganozinc reagents as primary organometallics, 3 and since this first report, in 1993, 3 this combination of a chiral phosphorus ligand and dialkyl zincs has found widespread use, 4-8 although the reaction could be also promoted by non-phosphorus ligands. 9 Typically, cyclohexenone has served as representative Michael acceptor (Scheme 1) with most often Cu(OTf) 2 as copper source (catalyst loading 0.5-2%), in toluene or CH 2 Cl 2 as solvent. Scheme 1Among the many ligands, which have been shown to be efficient, the ones based on a modular concept are of prime importance. Thus, a TADDOL or binaphthol moiety forms a ring with the phosphorus atom, whereas a chiral alcohol or amine is fixed on the exocyclic position ( Figure 1). This combination of two chiral moieties around the phosphorus atom allows for the formation of two diastereomeric ligands. The experimental results show that only one diastereomeric combination affords high enantioselectivities (the matched series) whereas the other one (the mismatched series) does not.For example, ligand L1 affords 96% ee for the conjugate addition of diethylzinc onto cyclohexenone (Scheme 1), whereas the mismatched ligand L1' affords a racemic product. 4d,4e Similarly, ligand L2 affords 98% ee 5 (75% for the mismatched L2') and ligand L3 52% ee 6 (9% for the mismatched L3') for the same reaction. Both mismatched ligands afforded, however, the opposite enantiomer, showing that the binaphthol unit is imposing the absolute stereochemistry of the conjugate adduct. Such behavior of diastereomeric ligands is not unknown and some examples have been reported. 10In the course of our studies to find new ligands, we prepared an equimolecular mixture of ligands L2 and L2', starting from racemic binaphthol. When the reaction was performed using this mixture (Scheme 2), ethyl cyclohexanone was obtained in quantitative yield and with an ee of 66%, corresponding to the enantiomer given by L2! Thus, although each ligand should afford an opposite enantiomer, the matched ligand L2 is largely more efficient and overcomes the mismatched L2'. 11