R. H. Schlessinger

The vinylogation of aldehydes: An improved method for the preparation of alpha formylethylidenetriphenylphosphorane, and an improved alpha silyl imine reagent of propionaldehyde

Abstract A high yield preparation of α-formylethylidenetriphenylphosphorane from the ethyltriphenylphosphonium iodide and ethyl formate Is reported. The α-triethylsilyl t -butylimine of propionaldehyde is a thermally stable and easily purified reagent that smoothly olefinates aldehydes and ketones.

The synthesis of either (+) or (−) trans-2,5-dimethylpyrrolidine

Abstract Trans -2,5-dimethylpyrrolidine, in either optical series, is prepared starting from D or L -alanine in an efficient and reasonably brief reaction sequence.

Highly diastereoselective alkylation reactions of vinylogous urethanes derived from simple tetronic acids

Abstract The lithium enolates generated from the tetronic acid derived vinylogous urethanes 3 and 4 have been found to undergo alkylation reactions with a variety of electrophiles to give products with predictable stereochemistry accompanied by very high diastereoselectivity.

Diastereoselective Diels-Alder reactions of nonracemic 3- and 4-amino furans bound to polystyrene. A comparison of these reactions to their solution state analogues

Abstract The potassium enolates of the 3 and 4-amino furanones 4 and 12 have been silylated with polymer 3 . The resulting polymer-bound nonracemic amino furans 5 and 11 were found to undergo the Diels-Alder reaction with a variety of dienophiles. The endo -adducts derived from methyl acrylate were both directly cleaved from the polymer and or synthetically manipulated and then cleaved from the polymer to demonstrate their formation in >99% de .

ASYMMETRIC TOTAL SYNTHESIS OF (+)-PHOMALACTONE, (+)-ACETYLPHOMALACTONE AND(+)-ASPERLIN UTILIZING A NOVEL SYN-SELECTIVE C4-OXA-VINYLOGOUS URETHANE

Abstract The total synthesis of three natural products isolated from Nigrospora sp., Phoma sp., and Aspergillus nidulans 1 starting from an aldol reaction with a homochiral C 4 -oxa-vinylogous urethane is described. Inherent stereoselectivity of the aldol reaction and overall alacrity of molecular construction are discussed.

SYNTHESIS OF THE C19 THROUGH C27 SEGMENT OF OKADAIC ACID USING VINYLOGOUS URETHANE ALDOL CHEMISTRY : PART III

Abstract The synthesis of the C-19 through C-27 segment of the marine natural product okadaic acid was accomplished employing a highly enantio- and diasteroselective aldol coupling reaction of a chiral vinylogous urethane lactone enolate. The remainder of the carbon skeleton of this segment was constructed by a diastereoselective γ-oxygenated allylstannane addition. Formation of the tetrahydropyran ring was achieved utilizing a stereoselective electrophilic cyclization.

A VINYLOGOUS URETHANE APPROACH TOWARDS THE SYNTHESIS OF OKADAIC ACID. CONSTRUCTION OF THE C9-C18 FRAGMENT. PART II

Abstract A diastereo- and enantioselective acylation-reduction sequence of a vinylogous urethane lactone silylketene acetal sets the initial stereocenter in this approach towards the C9-C18 fragment of okadaic acid. The remainder of the stereocenters are installed via a silyl cuprate conjugate addition trapping sequence, and a lactol is transformed to a tetrahydrofuran by addition of a propargyl aluminum species. A novel tetrabydrofuran ring opening reaction utilizing dimethyl boron bromide is also illustrated.

A non-congener based synthesis of L-(-)-rhodinose and of a C4 hydroxyl protected derivative

Abstract A practical five step construction of the L-(-)-rhodinose derivative 1 and of L-(-)-rhodinose ( 2 ) from O-benzyl (S)-ethyl lactate is described. Optical rotations and other data for both 1 and 2 as well as for intermediates leading to them are provided.

An enantioselective solutions towards synthesizing “skip” 1,3 dimethyl stereocenters. A synthesis of 4S(2E,4R∗,6R∗)-4,6-Dimethyl-2-octenoic acid

Abstract A versatile method of synthesizing “skip” 1,3 dimethyl stereocenters via an enantioselective aldol reaction followed by stereoselective catalytic hydrogenation produces three syn contiguous chiral centers. Barton deoxygenation of the intermediary hydroxyl group provides the desired skip 1,3 dimethyl array.

A synthesis of the tetramic acid subunit of streptolydigin: A reactivity definition of this subunit as an Emmons reagent

Abstract A practical and brief construction of the tetramic acid-derived Emmons reagent 3 is described. The reactivity of this substance with aldehydes has been examined with respect to its use in a synthesis of the antibiotic streptolydigin.