Synthetic approaches to bicyclomycin I. Prepration of monocylic intermediates by retrograde Michael cleavage of 6-alkyl-6-methoxyhexahydro-3H-thiazolo [3,4-a]pyrazine-5,8-diones.

The syntheses of N-protected-3-(hydroxypropyl)-3-methoxy-6-alkylidine piperazine-2,5-diones are described, in relation to an approach to bicyclomycin. A chemoselective Grignard reaction and a novel diastereoselective retrograde Michael cleavage highlight the sequence.     

Vitamin D and click chemistry. Part 1: A stereoselective route to vitamin D analogues with triazole rings in their side chains

Efficient preparation of vitamin D CD ring system synthons with triazole rings in their side chains is based on the formation of the triazole ring from a [3+2]-cycloaddition of a vitamin D side chain terminal azide with a terminal acetylene.     

UVA II Exposure of Human Skin Results in Decreased Immunization Capacity, Increased Induction of Tolerance and a Unique Pattern of Epidermal Antigen-Presenting Cell Alteration

Abstract— The risks incurred from increased exposure to UVA II (320-340 nm) (i.e. during sunscreen use and extended outdoor exposure, tanning parlors) are not well understood. Therefore, we explored the effects of UVA II on skin immune responses in humans. After a single local exposure (4 minimum erythemal dose [MED]) using a xenon arc lamp filtered with a narrow bandpass filter (335 ± 5 nm full width at half maximum), individuals were contact-sensitized with dinitrochlorobenzene (DNCB) through a UVA II exposure site or through normal skin. UVA II induced a marked decrease in the magnitude of skin immune responses (P < 0.0001). The UVA II group had only 29% successful sensitizations, as compared to 83% in the control group. The percentage of individuals who remained tolerant to DNCB after two sensitizations was 23.6% for the UVA II-exposed group, as compared to 3.8% in the controls (P= 0.006). UVA II also uniquely altered the type of antigen-presenting cells present in the epidermis. Human leukocyte antigen (HLA)-DR+ cells in control epidermal cell suspensions (C-EC) comprised a single, homogeneous population of Langerhans cells (LC) with the phenotype: CD1a^hi DR^mid CD11b^? CD36^? (1.5 ± 0.3% of EC). UVA II irradiation reduced the number of such LC to 0.6 ± 0.2% of EC. Although cells expressing the macrophage phenotype: CD1a DR^hi CD11b+ CD36+ were increased in UVA II skin, relative to C-EC, these comprised only 10.1 ± 6.1% of the DR+ cells, which is less than that after UVB exposure. Also distinct from UVB, a third population was found in UVA II-EC, which exhibited a novel phenotype: CD1a+ DR+ CD36+ CDllb+; these comprised 11.1 ± 6.9% of the DR+ UVA II-EC. In conclusion, despite the above differences in infiltrating DR cells, both UVB and UVA II reduce the skin's ability to support contact sensitization, induce active suppression (tolerance) and induce a reduction in LC.     

Misconceptions on Pollution and the Causes of Cancer

The public has numerous misconceptions about the relationship between environmental pollution and human cancer. Underlying these misconceptions is an erroneous belief that nature is benign. In this article we highlight eight of these misconceptions and describe the scientific information that undermines each one.     

On the variational characterization and convergence of bivariate splines

It is shown that bivariate interpolatory splines defined on a rectangleR can be characterized as being unique solutions to certain variational problems. This variational property is used to prove the uniform convergence of bivariate polynomial splines interpolating moderately smooth functions at data which includes interpolation to values on a rectangular grid. These results are then extended to bivariate splines defined on anL-shaped region.This research was supported by a University of Kansas General Research Grant.