2-Methylene-4-butyrolactones were conveniently synthesized by treatment of an aldehyde with 2-carboethoxyallyl(-ic) bromide and metallic tin (and aluminum) in good yields. Protolichesterinic acid was synthesized by employing the method.
ammonia. The C=C in the racemic diester 19 was ozonolysed and the diketone converted by Beckmannrearrangement into the bis-lactam . Reduction of the bis-lactam with lithium aluminium hydride and intramolecular nucleophilic displacement gave racemic sparteine 1. Some ideas for making this synthesis amenable to a synthesis of enantiomerically enriched sparteine are presented.
The Diels-Alder reaction of some bromo derivatives of the itaconic acid with cyclopenta-1,3-diene gave a simple access to precursors of spherical polyols of synthetic interest. bicyclic compounds - Diels-Alder reaction - ozonolysis - stereoselective synthesis - protecting groups
A construction of the pentacyclic framework of sterepolide is described. Stereochemistry of the structure 2 is well established by unequivocal reaction sequences. The Diels-Alder adducts are transformed into a key intermediate 15 by a few steps. Conversion of 15 to 2 is effected by a Nazarov cyclization and subsequent selective reduction of the lactone carbonyl group.
Amino-sulfhydryl cross-linking reagents that are cleavable under mildly acidic conditions are disclosed. Also disclosed are methods of making the cross-linkers, as well as methods of using the cross-linkers, e.g., to deliver a biologically active substance across the membranes of selected cells in a heterogeneous cell population; once inside the cell the active substance is released, intact, by the transient, mild acidity of certain cell structures. Finally, a method of characterizing complex multi-chain protein structures is disclosed.