Remote Stereocontrol in the Ireland-Claisen Rearrangement by δ-Alkoxy Group.

Remote stereocontrol in the Ireland-Claisen rearrangement using a chiral acetonide that serves as internal stereocontrol element is an effective and general method for chirality transfer from a δ-hydroxyl group in the allylic alcohol unit. This strategy circumvents the need for redundant chirality at the α-position allylic alcohol, while simultaneously producing a terminal alkene that can streamline synthetic applications and complex molecule synthesis planning.

Patency of the Internal Iliac Artery after Placement of Common and External Iliac Artery Stents.

BACKGROUND: Treatment of severe aortoiliac occlusive disease (AIOD) frequently requires long-segment stenting of the common and external iliac arteries (CIA and EIA, respectively). This study aims to analyze the patency of the internal iliac artery (IIA) after placement of a CIA and EIA stents across the orifice. METHODS: A retrospective analysis of all patients who underwent de novo ipsilateral stent placement in the CIA and EIA between 2006 and 2013 was performed. Kaplan-Meier analysis was used to analyze patency of the IIA, and Cox proportional hazard models were used to identify characteristics associated with occlusion. RESULTS: We identified 77 patients and 93 limbs where ipsilateral CIA and EIA stents were placed. Preintervention angiographic review found 52 cases of a patent ipsilateral IIA where stents were placed across the origin of the IIA in 31 cases and staggered across the orifice in 20 limbs. Kaplan-Meier analysis demonstrated a 37% patency in limbs where the stent covered the IIA orifice compared to 78% patency in uncovered arteries (P = 0.04). New-onset buttock claudication developed in 4 patients, 2 with patent IIAs and 2 with occluded. New-onset impotence also developed in 3 patients with occluded IIA and 5 patients with patent IIAs. CONCLUSIONS: Placement of stents across the origin of the IIA may not result in immediate occlusion, but long-term patency of covered IIAs is decreased compared to uncovered IIAs. This study is limited by a small sample size, but when treating AIOD, coverage of the internal iliac origin should be avoided to maintain patency of the pelvic circulation.

Development and characterization of amino donor-acceptor Stenhouse adducts.

Donor-acceptor Stenhouse adducts (DASAs) are molecular photoswitches spurring wide interest because of their dynamic photophysical properties, complex photoswitching mechanism, and diverse applications. Despite breakthroughs in modularity for the donor, acceptor, and triene compartments, the backbone heteroatom remains static due to synthetic challenges. We provide a predictive tool and sought-after strategy to vary the heteroatom, introduce amino DASA photoswitches, and analyze backbone heteroatom effects on photophysical properties. Amino DASA synthesis is enabled by aza-Piancatelli rearrangements on pyrrole substrates, imparting an aromaticity-breaking rearrangement that capitalizes on nitrogen's additional bonding orbital and the inductive properties of sulfonyl groups. Amino DASA structure is confirmed by single crystal X-ray diffraction, the photochromic properties are characterized, and the photoswitch isomerization is investigated. Overall, the discovered pyrrole rearrangement enables the study of the DASA backbone heteroatom compartment and furthers our insight into the structure-property relationship of this complex photoswitch.