Stereodivergent synthesis with a programmable molecular machine
Authors: Salma Kassem, Alan T. L. Lee, David A. Leigh, Vanesa Marcos, Leoni I. Palmer, Simone Pisano
Publication Date: 21 September, 2017
Department of: Chemistry
Building with a molecular robot
A ‘molecular assembler’ is a hypothetical futuristic concept for a ‘nanobot’ that is ‘able to guide chemical reactions by positioning reactive molecules with atomic precision’, originally proposed by the futurist K. Eric Drexler who was inspired by Richard P. Feynman’s celebrated lecture ‘There’s Plenty of Room at the Bottom’. Now scientists at the University of Manchester have developed a molecular robot that moves a substrate between different activating sites in order to achieve different product outcomes from chemical synthesis. The molecular robot can be programmed to selectively produce, in a sequential one-pot operation, any one of four possible diastereoisomers from a tandem reaction process, including compounds that cannot be made through conventional iminium-enamine organocatalysis. Each molecular robot manipulates a single substrate molecule, but the process is massively paralleled with more than a billion billion (i.e., 1018) molecular robots operating simultaneously.
These first generation machines augur well for the future development of small-molecule robots that can be programmed to manipulate substrates to control synthesis in a form of mechanosynthesis (that is, the use of mechanical constraints to direct reactive molecules to specific molecular sites), in a manner reminiscent of the way that molecular construction is carried out in biology.
- This nanobot is the first that can be programmed to build different molecules
- The molecular robot is only 2 nanometers (that is 2 millionths of a millimetre) long.
- ‘diastereoisomers’ are molecules which have the same atom connectivity but have some of the chemical groups held in different positions
- ‘iminium-enamine organocatalysis’ is a type of catalysis promoted by nitrogen-containing organic molecules