The pressing global issue of food insecurity due to population growth, diminishing land and variable climate can only be addressed in agriculture by improving both maximum crop yield potential and resilience. Genetic modification is one potential solution, but has yet to achieve worldwide acceptance, particularly for crops such as wheat. Trehalose-6-phosphate (T6P), a central sugar signal in plants, regulates sucrose use and allocation, underpinning crop growth and development. Here we show that application of a chemical intervention strategy directly modulates T6P levels in planta. Plant-permeable analogues of T6P were designed and constructed based on a 'signalling-precursor' concept for permeability, ready uptake and sunlight-triggered release of T6P in planta. We show that chemical intervention in a potent sugar signal increases grain yield, whereas application to vegetative tissue improves recovery and resurrection from drought. This technology offers a means to combine increases in yield with crop stress resilience. Given the generality of the T6P pathway in plants and other small-molecule signals in biology, these studies suggest that suitable synthetic exogenous small-molecule signal precursors can be used to directly enhance plant performance and perhaps other organism function.

Thiourea mediates cooperative glycosidation through hydrogen bonding. N,N'-Diarylthiourea as cocatalyst enforces an SN2-type acid-catalyzed glycosidation even at room temperature (see scheme; Bn=benzyl). From O-(α-glycosyl) trichloroacetimidates as glycosyl donors and various acceptors, β-glycosides are preferentially or exclusively obtained.

Under pre-activation glycosylation conditions, the 4,6-di-O-acetyl-N-acetyloxazolidinone protected donor afforded either excellent beta- or alpha-stereoselectivity simply by means of the addition of hindered base TTBP or the absence of base, leading to the controllable stereochemistry of coupling reactions.

Adduct formation between alcohols as glycosyl acceptors and phenylsilicon trifluoride (PhSiF3) as catalyst permits acid‐base‐atalyzed glycosidations with O‐glycosyl trichloroacetimidates as glycosyl donors. In this way, from various glycosyl donors and acceptors 1,2‐trans‐ and some 1,2‐cis‐glycosides could be obtained with high anomeric selectivity. A preference for an intramolecular bimolecular nucleophilic substitution (SN2‐type) reaction course with concomitant donor and acceptor activation is supported by the results.

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Catalytic or stoichiometric amounts of Lewis acids were found to be very effective α-directing additives in the stereoselective glycosylations of diverse 2,3-O-carbonateprotected glucose and galactose thioglycoside donors by preactivation protocol. The poor stereoselectivities of 4,6-di-Oacetyl-2,3-O-carbonate protected thioglycoside donors in glycosyl coupling reactions were greatly improved, and excellent αstereoselectivities were achieved by the addition of 0.2 equiv of BF 3 •OEt 2 . On the other hand, the β-selectivities of 4,6-di-Obenzyl-2,3-O-carbonate-protected thioglucoside donor toward glycosylations were reversed completely to the α-selectivities by the use of 1 equiv of SnCl 4 , making the stereoselectivity controllable. Furthermore, the poor stereoselectivities of 4,6-di-O-benzyl-2,3-O-carbonate-protected thiogalactoside donor in glycosylations were also improved by using SnCl 4 as additive.

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2‐O‐Propargyl‐substituted glycosyl donors and O‐(2‐azidobenzyl)‐substituted acceptors having a vicinal hydroxy group readily underwent the click reaction. Intramolecular glycosidation with N‐iodosuccinimide/trifluoromethansulfonic acid as the activating system afforded β‐(1–3)‐ and α‐(1–2)‐linked disaccharides as part of 14‐membered macrocycles. Descriptors for these reactions are proposed that consider the donor and acceptor attachment sites and the stereochemistry of the functional groups. Investigation of the influence of 2‐O‐linked 1‐aryl‐1,2,3‐triazol‐4‐ylmethyl groups, as contained in the spacer, on the anomeric selectivity exhibited no anchimeric assistance. In addition, it was shown that the spacer group can be readily cleaved under Birch reduction conditions.