Synthesis of γ-, δ-, and ε-Lactams by Asymmetric Transfer Hydrogenation of N-(tert-Butylsulfinyl)iminoesters

Highly enantiomerically enriched γ- and δ-lactams have been prepared by a simple and very efficient procedure that involves the asymmetric transfer hydrogenation of N-(tert-butylsulfinyl)iminoesters followed by desulfinylation of the nitrogen atom and spontaneous cyclization to the desired lactams during the basic workup procedure. Five- and six-membered ring lactams bearing aromatic, heteroaromatic, and aliphatic substituents have been obtained in very high yields and ee’s up to >99%. A slight modification of the procedure also allowed the preparation of ε-lactams in good yields and very high enantioselectivities. Both enantiomers of the final lactams could be prepared with equal efficiency by changing the absolute configuration of the sulfinyl chiral auxiliary

Retinoid X Receptor Agonists Upregulate Genes Responsible for the Biosynthesis of All-Trans-Retinoic Acid in Human Epidermis.

UAB30 is an RXR selective agonist that has been shown to have potential cancer chemopreventive properties. Due to high efficacy and low toxicity, it is currently being evaluated in human Phase I clinical trials by the National Cancer Institute. While UAB30 shows promise as a low toxicity chemopreventive drug, the mechanism of its action is not well understood. In this study, we investigated the effects of UAB30 on gene expression in human organotypic skin raft cultures and mouse epidermis. The results of this study indicate that treatment with UAB30 results in upregulation of genes responsible for the uptake and metabolism of all-trans-retinol to all-trans-retinoic acid (ATRA), the natural agonist of RAR nuclear receptors. Consistent with the increased expression of these genes, the steady-state levels of ATRA are elevated in human skin rafts. In ultraviolet B (UVB) irradiated mouse skin, the expression of ATRA target genes is found to be reduced. A reduced expression of ATRA sensitive genes is also observed in epidermis of mouse models of UVB-induced squamous cell carcinoma and basal cell carcinomas. However, treatment of mouse skin with UAB30 prior to UVB irradiation prevents the UVB-induced decrease in expression of some of the ATRA-responsive genes. Considering its positive effects on ATRA signaling in the epidermis and its low toxicity, UAB30 could be used as a chemoprophylactic agent in the treatment of non-melanoma skin cancer, particularly in organ transplant recipients and other high risk populations

UAB30 dose-dependent induction of retinoid metabolic genes.

<p>QPCR analysis was performed as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0153556#pone.0153556.g003" target="_blank">Fig 3</a>. Error bars represent mean ± SEM of three independent rafts. *p<0.05; **p<0.01.</p

ATRA concentration in samples of skin rafts.

<p>ATRA concentration in samples of skin rafts.</p

QPCR analysis of gene expression in skin rafts treated with UAB30 or Bexarotene.

<p>Three individual rafts were used for each treatment. QPCR analysis for each raft was done in triplicate. Data were normalized per peptidylprolyl isomerase A (<i>PPIA</i>, cyclophilin A) and represent average ± SEM. <i>DHRS9</i>, dehydrogenase/reductase member 9 (SDR9C4); <i>DHRS3</i>, dehydrogenase/reductase member 3 (SDR16C1, also known as retSDR1); <i>RDH10</i>, retinol dehydrogenase 10 (SDR16C4); <i>RARγ</i>, retinoic acid receptor γ; <i>LRAT</i>, lecithin retinol acyltransferase; <i>STRA6</i>, stimulated by retinoic acid gene 6; <i>MUC21</i>, mucin 21; <i>GABRP</i>, γ-aminobutyric acid (GABA) A receptor π; <i>FLG</i>, filaggrin; <i>CYP26B1</i>, cytochrome P450 26B1; <i>MCM7</i>, minichromosome maintenance complex component 7; <i>CRBP1</i>, cellular retinol binding protein type 1. Symbol * indicates statistically significant differences in expression of genes in UAB30-treated rafts <i>versus</i> vehicle-treated rafts. Symbol # indicates the differences in expression of genes in bexarotene-treated rafts <i>versus</i> UAB30-treated rafts. *and ^# indicate p values <0.05; ** and ^## indicate p values <0.005.</p

QPCR analysis of gene expression in skin rafts treated with different doses of UAB30.

<p>QPCR analysis was performed as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0153556#pone.0153556.g003" target="_blank">Fig 3</a>. Error bars represent mean ± SEM of three independent rafts. *p<0.05; **p<0.01.</p

H&E staining of skin rafts treated with UAB30.

<p><b>A</b>, Human organotypic skin raft cultures were grown in the presence of 0–10 μM UAB30. <b>B</b>, Primary neonatal keratinocytes (PHKs) were infected with Moloney murine leukemia retroviral vector pBabe puro expressing RDH10 and selected with 1.5 μg/ml puromycin for 2 days as described previously [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0153556#pone.0153556.ref051" target="_blank">51</a>]. Retrovirus-transduced PHKs were cultured at the medium-air interface to produce RDH10 transgenic rafts. Differently colored brackets demarcate the layers of epidermis: cornified (red), granular (orange), spinous (purple), and basal (gray). Note the similarly increased thickness of the basal layer (gray bracket) and reduced differentiation to cornified layer (red bracket) in rafts treated with 10 μM UAB30 as compared with RDH10-overexpresing rafts.</p

HPLC analysis of retinyl esters in UAB30-treated skin rafts.

<p>Retinyl esters were extracted from three samples each containing five pooled UAB30-treated or DMSO-treated skin rafts. Data represent mean ± SEM; **p<0.01.</p