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1.
Tetrahedron Lett ; 1152023 Jan 31.
Article in English | MEDLINE | ID: mdl-36777739

ABSTRACT

A concise total synthesis of (±)-N-methyldibromoisophakellin, a member of the monomeric pyrrole-aminoimidazole alkaloid family isolated from the marine sponge Stylissa carbica, was achieved via a net [3+2] cycloaddition to install the cyclic guanidine. This ring annulation employs a 2-amido-1,3-aminoallyl cation obtained under oxidative conditions from variously N-substituted guanidines which in one instance led to isolation of a tetracycle bearing a carbinolamine center through subsequent benzylic oxidation. Finally, the serendipitous formation of a unique, related alkenyl guanidine, N-methylugibohlin, achieved via ring opening of cyclic guanidine under acidic conditions suggests that ugibohlin may be an artifact of isolation.

2.
Angew Chem Int Ed Engl ; 61(46): e202210821, 2022 11 14.
Article in English | MEDLINE | ID: mdl-36121442

ABSTRACT

Described herein are the first total syntheses of (±)-dracocephalone A (1) and (±)-dracocequinones A (4) and B (5). The synthesis was initially envisioned as proceeding through an intramolecular isobenzofuran Diels-Alder reaction, a strategy that eventually evolved into a Lewis acid-promoted spirocyclization. This highly diastereoselective transformation set the stage for trans-decalin formation and a late-stage Suárez oxidation that produced a [3.2.1] oxabicycle suited for conversion to 1. Brønsted acid-mediated aromatization, followed by a series of carefully choreographed oxidations, allowed for rearrangement to a [2.2.2] oxabicycle poised for conversion to 4 and 5.


Subject(s)
Lewis Acids , Stereoisomerism , Cycloaddition Reaction , Oxidation-Reduction
3.
J Am Chem Soc ; 143(15): 6006-6017, 2021 04 21.
Article in English | MEDLINE | ID: mdl-33825475

ABSTRACT

The sesquiterpene-tropolones belong to a distinctive structural class of meroterpene natural products with impressive biological activities, including anticancer, antifungal, antimalarial, and antibacterial. In this article, we describe a concise, modular, and cycloaddition-based approach to a series of sesquiterpene mono- and bistropolones, including (-)-epolone B, (+)-isoepolone B, (±)-dehydroxypycnidione, and (-)-10-epi-pycnidione. Alongside the development of a general strategy to access this unique family of metabolites were computational modeling studies that justified the diastereoselectivity observed during key cycloadditions. Ultimately, these studies prompted stereochemical reassignments of the pycnidione subclass and shed additional light on the biosynthesis of these remarkable natural products.


Subject(s)
Sesquiterpenes/chemistry , Tropolone/chemistry , Biological Products/chemical synthesis , Biological Products/chemistry , Cycloaddition Reaction , Density Functional Theory , Heterocyclic Compounds, 4 or More Rings/chemical synthesis , Heterocyclic Compounds, 4 or More Rings/chemistry , Molecular Conformation , Monocyclic Sesquiterpenes/chemical synthesis , Monocyclic Sesquiterpenes/chemistry , Sesquiterpenes/chemical synthesis , Stereoisomerism , Tropolone/analogs & derivatives , Tropolone/chemical synthesis
4.
Sci Transl Med ; 8(366): 366ra165, 2016 11 23.
Article in English | MEDLINE | ID: mdl-27881826

ABSTRACT

Capabilities in health monitoring enabled by capture and quantitative chemical analysis of sweat could complement, or potentially obviate the need for, approaches based on sporadic assessment of blood samples. Established sweat monitoring technologies use simple fabric swatches and are limited to basic analysis in controlled laboratory or hospital settings. We present a collection of materials and device designs for soft, flexible, and stretchable microfluidic systems, including embodiments that integrate wireless communication electronics, which can intimately and robustly bond to the surface of the skin without chemical and mechanical irritation. This integration defines access points for a small set of sweat glands such that perspiration spontaneously initiates routing of sweat through a microfluidic network and set of reservoirs. Embedded chemical analyses respond in colorimetric fashion to markers such as chloride and hydronium ions, glucose, and lactate. Wireless interfaces to digital image capture hardware serve as a means for quantitation. Human studies demonstrated the functionality of this microfluidic device during fitness cycling in a controlled environment and during long-distance bicycle racing in arid, outdoor conditions. The results include quantitative values for sweat rate, total sweat loss, pH, and concentration of chloride and lactate.


Subject(s)
Colorimetry/methods , Microfluidics/instrumentation , Sweat/chemistry , Wearable Electronic Devices , Adolescent , Adult , Aged , Biosensing Techniques , Child , Chlorides/chemistry , Equipment Design , Female , Glucose/chemistry , Humans , Hydrogen-Ion Concentration , Image Processing, Computer-Assisted , Lab-On-A-Chip Devices , Lactic Acid/chemistry , Male , Middle Aged , Smartphone , User-Computer Interface , Young Adult
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