30 research outputs found
Stereoselective synthesis towards (+)-trans-kumausyne employing vinylogous Mukaiyama type reaction on an α-chloro sulfide
1199-1205A stereoselective synthesis towards (+)-trans-kumausyne is disclosed. The key steps of the synthesis include stereoselective C-C formation employing vinylogous Mukaiyama type reaction of an α-chloro sulfide with 2-trimethylsiloxy furan and base-catalyzed isomerization followed by intramolecular oxa-Michael reaction
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A Wireless Energy Harvester for Powering Event-driven Internet-of-things Applications and Battery Charging
The need for sustainably powering unobtrusive internet-of-things applications has led to an interest in energy harvesting. Particularly, the proliferation of wireless communication and devices in the 2.4 GHz Industrial Scientific�c Medical (ISM) band creates an opportunity to leverage commonly used devices for RF powering. This dissertation presents a low-quiescent-power energy harvester architecture and techniques for enhancing wireless powering range and demonstrates long-range RF-powered sensor operation and chip-scale battery charging in 65nm CMOS.
First, the challenges in long-range RF-powering at 2.4 GHz are presented in the context of the Federal Communications Commission (FCC) regulations. Techniques and recti�fier architectures employed to improve harvester sensitivity are then discussed followed by trade-offs of long-range powering on system design.
The design of a cm-scale RF-energy harvester for RF powering in the 2.4 GHz ISM band is described. The harvester includes a loop antenna, recti�fier and boost converter. The antenna and recti�fier are codesigned to maximize passive gain for a small constrained antenna area. The boost converter is designed while considering cold-start operation and nanowatt-scale available power from the recti�fier for RF
incident power <-33 dBm. Low-power design in the power management unit and converter leads to 960pW quiescent power. The harvester implementation in 65-nm CMOS occupies 1.6 sq. mm while the antenna occupies 1.27 sq. cm. The proposed design optimization approach leads to a sensitivity of -33dBm in cold start and -36dBm
in the primary mode for 1V output. Measurements using a commercial WiFi TX demonstrate ranges of up to 1.25m for 14dBm output power with 1.3% TX duty-cycling in WiFi access-point mode, demonstrating the feasibility of powering sensors from RF power beacons in the 2.4 GHz ISM band as well as from background WiFi transmissions.
A 2.4GHz pH-sensor radio for wireless biomedical and environmental sensing demonstrating the feasibility of long-range RF-powered sensors is presented. A 960 pW-quiescent-power harvester combined with a MIMO RF-powering approach is used to further enhance RF powering range by 40% without handshaking between MIMO TX
and sensor node. The harvester achieves -36dBm cold-start sensitivity with respect to each MIMO TX element corresponding to 4m range with 16dBm TX. The 65nm CMOS harvester powers a 400nW wake-up RX, 1.45mW Class-D TX and 30 microwatt sensor interface, and the complete SoC occupies 1.9 sq. mm.
An end-to-end 2.4 GHz, RF-powered FCC-compatible battery-charger IC for long-range miniature chip-scale battery charging is presented to achieve sustainable powering for IoT sensors. A bulk-connected recti�er is used to improve efficiency by reducing leakage and an integrated rectifier resonant-frequency tuning loop is employed to maximize passive gain by tracking input RF frequency for frequency-hopped
source. A boost converter placed in cascade with the recti�fier harvests efficiently across -27dBm to -17dBm RF available power and cold-starts without drawing any power from the battery, achieving state-of-the-art net positive charging for -21.5dBm incident power and 4.18% duty-cycled FCC-compliant frequency-hopped RF input assuming a steady-state 100 nA load
Stereoselective preparation of a key intermediate toward the synthesis of nelfinavir
821-828A stereoselective
synthesis of an intermediate that can be elaborated into the potent
HIV-protease inhibitor, nelfinavir, is described. The key step of the reaction
sequence is the stereoselective preparation of a bromosulfonamide from an
olefin using the sulfilimine moiety as an intramolecular nucleophile
Approaches to the stereoselective synthesis of (+)-lactacystin utilizing organocatalytic reactions
1075-1085Efforts toward a
stereoselective synthetic route to (+)-lactacystin based on organocatalytic
transformations and intramolecular amino hydroxylation for creating the
tetrasubstituted stereogenic center are described. Tethered aminohydroxylation
of an allylic carbamate following Donohue's protocol affords a regioisomeric
amino alcohol derivative, while Lewis acid promoted epoxide opening by a
trichloroacetimidate yields a tetrahydrofuran derivative
A 2.4-GHz Wideband Wireless Harvester With Integrated Autonomous RF Input-Frequency Tracking for FCC-Compatible Chip-Scale Battery Charging
RF-powered Internet of Things (IoT) sensor duty cycles are limited due to low available energy at long range in the absence of a battery. Additionally, RF energy harvesters with high- interfaces between the antenna and rectifier suffer from poor sensitivity for RF input frequencies outside their narrow bandwidth. In this article, we address these challenges and present a channel-agnostic far-field 2.4-GHz energy harvester achieving: 1) dynamic RF input frequency tracking for wideband sensitivity; 2) FCC-compatible frequency-hopped input harvesting; and 3) optimal battery charging capability for powering energy-constrained IoT applications. An enhanced antenna-rectifier interface is designed with 2-dB better stand-alone sensitivity and lower leakage using a bulk-connected rectifier. Input frequency tracking is achieved over 15-MHz bandwidth using a fast-settling auto-zeroing amplifier that senses the rectifier’s first-stage output. Chip-scale pulsed battery charging is achieved from cold-start over RF available power ranging from −27 to −17 dBm with > 22% efficiency across the entire range. State-of-the-art battery charging is achieved at −21.5-dBm incident power and 4.18% duty cycled (1-h-per-day charging) FCC-compliant frequency-hopped RF input assuming a steady-state 100-nA load. The compact harvester IC occupies 2 mm2 in a 65-nm CMOS technology and the antenna and IC integrated together in a chip-on-board approach occupy 2.125 cm2 of PCB area
Stereoselective synthesis towards (+)-trans-kumausyne employing vinylogous Mukaiyama type reaction on an α-chloro sulfide
A stereoselective synthesis towards (+)-trans-kumausyne is disclosed. The key steps of the synthesis include stereoselective C-C formation employing vinylogous Mukaiyama type reaction of an α-chloro sulfide with 2-trimethylsiloxy furan and base-catalyzed isomerization followed by intramolecular oxa-Michael reaction
Toward a stereoselective synthesis of tetrahydroxy long chain base (LCB) and the synthesis of analogs of mannostatin A
559-579Efforts toward the stereoselective synthesis
of tetrahydroxy long chain base and analogs of mannostatin A are described. The
sulfinyl moiety has been efficiently utilized as an intramolecular nucleophile
for oxidative functionalization of an alkene and regioselective opening of an
epoxide. Nucleophilic addition to sulfinylimine has been used for the
introduction of amino stereogenic center. Pummerer reaction has not been
successful with a free N-H group at -carbon. Pummerer
reaction on a N,O-acetonide furnishes an aldehyde. Attempted Wittig olefination to
access the protected derivative of long chain base have failed. The analog of
mannostatin could not be prepared by intramolecular addition of a sulfinyl carbanion
to an imine but could be prepared by radical chemistry
Synthesis based on cyclohexadienes: Part 10 synthesis of 5,5-dimethyl-7-methoxy-4-oxatricyclo[4.3.1.0]decan-2-ones
Synthesis of 5, 5-dimethyl- 7-methoxy-4 -oxatricyclo[4,3,1,0(3,7)]- decan-2-one 3a, a novel heterocyclic ring system present in morellin 1, and its 3-substituted derivatives 3b-e, is described from the Diels-Alder adducts 7, available from 1-methoxycyclohexa-1,4-dienes 4. Two routes, which involved the halocyclisation and the oxidative addition, were investigated for the conversion of the adducts 7 into 3. While the halocyclisation method resulted in mixtures, excellent yields of the target molecule were obtained by the second method. Solvolysis of the bromoether 9 resulted in a mixture of rearranged products 10, 13, 15 and 16