Total Synthesis Without Protecting Groups: Pyrrolidines and Cyclic Carbamates

A protecting group free synthesis of 2,3-cis substituted hydroxypyrrolidines is reported. Two novel reaction methodologies allow for the stereoselective formation of cyclic carbamates from olefinic amines, and the formation of primary amines via a Vasella/reductive amination reaction, both performed in aqueous media

Applications and Limitations of the I₂‑Mediated Carbamate Annulation for the Synthesis of Piperidines: Five- versus Six-Membered Ring Formation

A protecting-group-free synthetic strategy for the synthesis of piperidines has been explored. Key in the synthesis is an I2-mediated carbamate annulation, which allows for the cyclization of hydroxy-substituted alkenylamines into piperidines, pyrrolidines, and furans. In this work, four chiral scaffolds were compared and contrasted, and it was observed that with both d-galactose and 2-deoxy-d-galactose as starting materials, the transformations into the piperidines 1-deoxygalactonorjirimycin (DGJ) and 4-epi-fagomine, respectively, could be achieved in few steps and good overall yields. When d-glucose was used as a starting material, only the furan product was formed, whereas the use of 2-deoxy-d-glucose resulted in reduced chemo- and stereoselectivity and the formation of four products. A mechanistic explanation for the formation of each annulation product could be provided, which has improved our understanding of the scope and limitations of the carbamate annulation for piperidine synthesis

Chimeric NOD2 Mincle Agonists as Vaccine Adjuvants

There is a need for improved vaccine adjuvants to augment vaccine efficacy. One way to address this is by targeting multiple immune cell pathogen recognition receptors (PRRs) using chimeric pathogen-associated molecular patterns (PAMPs). Conjugation of the PAMPs will ensure codelivery of the immunostimulatory molecules to the same cell, enhancing adjuvant activity. The macrophage inducible C-type lectin (Mincle) is a promising PRR for adjuvant development; however, no effective chimeric Mincle adjuvants have been prepared. We addressed this by synthesizing Mincle adjuvant conjugates, MDP-C18Brar and MDP-C18Brar-dilipid, which contain PAMPs recognized by Mincle and the nucleotide-binding oligomerization domain 2 (NOD2). The two PAMPs are joined by a pH-sensitive oxyamine linker which, upon acidification at lysosomal pH, hydrolyzed to release the NOD2 ligands. The conjugates elicited the production of Th1 and Th17 promoting cytokines in vitro, and when using OVA as a model antigen, exhibited enhanced T-cell-mediated immune responses and reduced toxicity in vivo, compared to the coadministration of the adjuvants

Chimeric NOD2 Mincle Agonists as Vaccine Adjuvants

There is a need for improved vaccine adjuvants to augment vaccine efficacy. One way to address this is by targeting multiple immune cell pathogen recognition receptors (PRRs) using chimeric pathogen-associated molecular patterns (PAMPs). Conjugation of the PAMPs will ensure codelivery of the immunostimulatory molecules to the same cell, enhancing adjuvant activity. The macrophage inducible C-type lectin (Mincle) is a promising PRR for adjuvant development; however, no effective chimeric Mincle adjuvants have been prepared. We addressed this by synthesizing Mincle adjuvant conjugates, MDP-C18Brar and MDP-C18Brar-dilipid, which contain PAMPs recognized by Mincle and the nucleotide-binding oligomerization domain 2 (NOD2). The two PAMPs are joined by a pH-sensitive oxyamine linker which, upon acidification at lysosomal pH, hydrolyzed to release the NOD2 ligands. The conjugates elicited the production of Th1 and Th17 promoting cytokines in vitro, and when using OVA as a model antigen, exhibited enhanced T-cell-mediated immune responses and reduced toxicity in vivo, compared to the coadministration of the adjuvants

Protecting-Group-Free Synthesis of Amines: Synthesis of Primary Amines from Aldehydes via Reductive Amination

New methodology for the protecting-group-free synthesis of primary amines is presented. By optimizing the metal hydride/ammonia mediated reductive amination of aldehydes and hemiacetals, primary amines were selectively prepared with no or minimal formation of the usual secondary and tertiary amine byproduct. The methodology was performed on a range of functionalized aldehyde substrates, including in situ formed aldehydes from a Vasella reaction. These reductive amination conditions provide a valuable synthetic tool for the selective production of primary amines in fewer steps, in good yields, and without the use of protecting groups

Chimeric NOD2 Mincle Agonists as Vaccine Adjuvants

There is a need for improved vaccine adjuvants to augment vaccine efficacy. One way to address this is by targeting multiple immune cell pathogen recognition receptors (PRRs) using chimeric pathogen-associated molecular patterns (PAMPs). Conjugation of the PAMPs will ensure codelivery of the immunostimulatory molecules to the same cell, enhancing adjuvant activity. The macrophage inducible C-type lectin (Mincle) is a promising PRR for adjuvant development; however, no effective chimeric Mincle adjuvants have been prepared. We addressed this by synthesizing Mincle adjuvant conjugates, MDP-C18Brar and MDP-C18Brar-dilipid, which contain PAMPs recognized by Mincle and the nucleotide-binding oligomerization domain 2 (NOD2). The two PAMPs are joined by a pH-sensitive oxyamine linker which, upon acidification at lysosomal pH, hydrolyzed to release the NOD2 ligands. The conjugates elicited the production of Th1 and Th17 promoting cytokines in vitro, and when using OVA as a model antigen, exhibited enhanced T-cell-mediated immune responses and reduced toxicity in vivo, compared to the coadministration of the adjuvants

DataSheet1_Water-soluble trehalose glycolipids show superior Mincle binding and signaling but impaired phagocytosis and IL-1β production.PDF

The tremendous potential of trehalose glycolipids as vaccine adjuvants has incentivized the study of how the structures of these ligands relate to their Mincle-mediated agonist activities. Despite this, structure-activity work in the field has been largely empirical, and less is known about how Mincle-independent pathways might be affected by different trehalose glycolipids, and whether Mincle binding by itself can serve as a proxy for adjuvanticity. There is also much demand for more water-soluble Mincle ligands. To address this need, we prepared polyethylene glycol modified trehalose glycolipids (PEG-TGLs) with enhanced water solubility and strong murine Mincle (mMincle) binding and signaling. However, only modest cytokine and chemokine responses were observed upon the treatment of GM-CSF treated bone-marrow cells with the PEG-TGLs. Notability, no IL-1β was observed. Using RNA-Seq analysis and a representative PEG-TGL, we determined that the more water-soluble adducts were less able to activate phagocytic pathways, and hence, failed to induce IL-1β production. Taken together, our data suggests that in addition to strong Mincle binding, which is a pre-requisite for Mincle-mediated cellular responses, the physical presentation of trehalose glycolipids in colloidal form is required for inflammasome activation, and hence, a strong inflammatory immune response.</p

Representative trehalose glycolipids, trehalose dibehenate (TDB), the natural product brartemicin, and a lipophilic derivative thereof, C18Brartemicin (C18Brar).

TDB and C18Brar are potent ligands for the C-Type lectin, Mincle.</p

Detailed procedure to synthesize C18Brar.

(DOCX)</p

IgG antibody responses to <i>M</i>. <i>haemolytica</i> and <i>M</i>. <i>ovipneumoniae</i> formulated in different adjuvants.

Mean (+SE) serum IgG antibody responses to M. haemolytica and M. ovipneumoniae in animals vaccinated with a mixture of M. haemolytica and M. ovipneumoniae whole cell antigens formulated with different adjuvants or given antigens (Ags) alone at week 0 and 3 (timing of vaccinations shown by arrows). Antibody responses were measured in serum samples collected at weeks 0, 3, 6, 9, and 13 using ELISA. Different alphabetical letters indicate significant differences (P < 0.05) between the groups, while the same letter indicates no significant difference between groups.</p