Control of the length of microfibers

Uniform polymeric microfibers of prescribed lengths were synthesized in microfluidic devices using two different approaches--valve actuation and pulses of ultraviolet (UV) light. The more versatile valve approach was employed to demonstrate control of the length of the microfiber as a function of the frequency of valve actuation.     

Efficient Synthesis of Substituted 3‐Azabicyclo[3.1.0]hexan‐2‐ones from 2‐Iodocyclopropanecarboxamides Using a Copper‐Free Sonogashira Coupling

The copper‐free Sonogashira coupling between N‐substituted cis‐ 2‐iodocyclopropanecarboxamides and terminal aryl‐, heteroaryl‐alkynes or enynes, followed by 5‐exo‐dig cyclization of the nitrogen amide onto the carbon–carbon triple bond, provides a remarkably efficient access to a variety of substituted 4‐methylene‐3‐azabicyclo[3.1.0]hexan‐2‐ones in excellent yields. Protonation of these latter enamides generates bicyclic N‐acyliminium ions that can be involved in Pictet–Spengler cyclizations leading to new 3‐azabicyclo[3.1.0]hexan‐2‐ones, possessing a quaternary stereocenter at C4, with high diastereoselectivities. This strategy constitutes an attractive complementary alternative to the classical route that relies on the addition of organometallic reagents to cyclopropyl imides.     

Total synthesis of (-)-spongidepsin

[structure: see text] A convergent and rapid stereoselective synthesis of (-)-spongidepsin has been achieved from the Roche ester in 14 steps with an overall yield of 13%.     

Rearrangement of homoallylic alcohols induced by DAST

[reaction: see text] Treatment of beta,gamma-unsaturated monoprotected 1,2-diols with diethylaminosulfur trifluoride (DAST) allows the stereoselective formation of beta,gamma-unsaturated aldehydes in good yields and with a good transfer of chirality.     

Enantio- and diastereoselective allylmetalations: an easy and efficient access to the AB spiroketal of spongistatin

[reaction: see text] A unique combination of highly enantio- and diastereoselective allylmetalations and a one-pot "desacetalization/spiroketalization" have been employed to synthesize the AB spiroketal fragment (C1-C13) of spongistatin in 15 steps and in excellent diastereoselectivity.