S. D. Gero

Synthesis and properties of a series of sterically hindered guanidine bases

By the reaction of Vilsmeier salts, derived from tetra-alkylureas or from tetra-alkylthioureas, with primary aliphatic amines, a series of sterically hindered penta-alkyl guanidines has been prepared. 2-t-Butyl-1′,1′,3″,3″-tetramethylguanidine and pentaisopropylguanidine combine ease of preparation with a range of resistance to alkylating agents. Preliminary experiments indicate that these inexpensive bases will be useful in organic synthesis.

Asymmetric synthesis of 1,3,4-trisubstituted and 3,4-disubstituted 2-azetidinones: strategy based on use of D-glucosamine as a chiral auxiliary in the Staudinger reaction

An efficient asymmetric approach to the synthesis of trisubstituted azetidin-2-ones is presented. The strategy relies on the use of ketene–imine cycloaddition between ketenes generated from phthalimidoacetic and methoxyacetic acids and a chiral Schiff base (3) derived from 3,4;5,6-di-O-isopropylidene-D-glucosamine propane dithioacetal (2) and cinnamaldehyde; the removal of the chiral auxiliary group by β-elimination is a noteworthy facet of this communication.

The synthesis and properties of a series of strong but hindered organic bases

A series of highly hindered N1,N2N2,N3,N3-penta-alkylguanidines has been synthesised from inexpensive starting materials; these strong bases show interesting effects in organic synthesis.

Synthetic methods for the preparation of D- and L-pseudo-sugars from D-glucose

Starting from D-glucose and using the Ferrier rearrangement to obtain the cyclohexanone (1), a convenient synthesis of crystalline pseudo-α-D-glucopyranose (15), its congeners (16) and (17), as well as their partially protected derivatives has been carried out.

Synthesis of carbocyclic analogues of D-glucosamine and L-idosamine from D-flucosamine

Derivatives of pseudo-D-glucosamine and pseudo-L-idosamine have been prepared from the chiral cyclohexanone (1) by a short sequence, including methoxy-methylenation or methylenation, followed by stereoselective oxymercuration or hydroboration, respectively of the resulting vinyl ether (2) and exocyclic methylene (3).

Total synthesis of (–)-ovalicine from L-quebrachitol

The first chiral synthesis of (–)-Ovalicine 1 from commercially available L-Quebrachitol in 16 steps and an overall yield of 3.5% is reported.

Stereospecificity in the synthesis of C-5 modified nucleosides using radical chemistry: furanosidic chain-lengthening through C-4

Radicals, generated from isopropylidene uronic esters of 2-thiopyridone, add readily to electron-poor alkenes in a stereospecific fashion, leading to functionalised chain-elongated furanosides and D-ribonucleosides through carbon-4; the acetal group has a directive effect in controlling chirality.

Studies related to maytansinoids

A rapid and high yielding route to optically active β-carbamoyloxy ketones of use in the synthesis of maytansinoids has been devised, starting from quinic acid.

Radical addition to vinyl phosphonates. A new synthesis of isosteric phosphonates and phosphonate analogues of α-amino acids

Derivatives of the phosphonic analogues of nucleotides and of side chain α-amino-acids can be readily prepared by irradiation of acyl-N-hydroxy-2-thiopyridones in the presence of diethylvinyl phosphonate.

Synthesis of branched-chain D-myo-inositols using the [3,3]sigmatropic Claisen rearrangement

A new and efficient synthesis of branched-chain cyclitols and their congeners utilizing a stereospecific Claisen rearrangement is reported.