Showing papers by "Andrew B. Holmes published in 1986"

A new synthetic method for the preparation of 2,8-disubstituted oxocane derivatives: synthesis of lauthisan and laurenan

Abstract: The cis-disubstituted oxocanes lauthisan (1) and laurenan (2) have been prepared from the lactone precursors (9b) and (9a) respectively by a sequence in which the key steps were methylenation and stereoselective hydroboration of the resulting enol ethers (11b) and (11a).

A new synthesis of eight-membered lactones containing a 5,6-double bond

Abstract: Claisen rearrangement of the vinyl ketene acetals (7; a, R = CH2OSiPh2 But, or b, R = n-pentyl) which are generated in situ by syn-elimination of the corresponding selenoxides (6a,b) in refluxing xylene gave the eight-membered lactones (8a,b).

A short stereoselective synthesis of (±)-carpamic acid

Abstract: The intramolecular N-alkenylnitrone cycloaddition of (9) is the key reaction in an efficient thirteen-step synthesis of carpamic acid (2) from methyl acetoacetate.

Studies on the synthesis of aphidicolin. Preparation of aromatic precursors for spirocyclic dienone formation

Abstract: Novel syntheses of the alkenediones (12; R = Me, or CH2Ph) and the corresponding epoxides (13) are described. Attempts to cyclise these compounds to the spirocyclic dienone (4) were unsuccessful. Model studies on the phenolic keto cyano toluene-p-sulphonate (24) showed that the cyclopropane (25) was formed preferentially. A variety of related model compounds (29), (31), (32), and (37) were prepared and studied, but none could be cyclised to spirocyclic dienones.

Studies on the synthesis of aphidicolin. The Diels–Alder route to spirocyclic intermediates

Abstract: The isopropylidene cyclohexylidenemalonates (6; R1= R2= H; R1, R2= OCH2CH2O; and R1, R2= SCH2CH2S) undergo cycloaddition with butadiene, 2-trimethylsilyloxybuta-1,3-diene, and 3-trimethylsilyloxypenta-2,4-diene to give the corresponding spirocyclic adducts (7; R1= R2= H), (11; R1, R2= OCH2CH2O; R1, R2= SCH2CH2S), and (23; R1, R2= OCH2CH2O; R1, R2= SCH2CH2S). The trimethylsilylenol ether (11; R1, R2= SCH2CH2S) was converted via compounds (12), (14), (15), (16), and (17) to the toluene-p-sulphonate (18) which undergoes base-catalysed intramolecular enolate alkylation to give the bicyclo[3.2.1 ]octanones (19) and (20) which serve as models for aphidicolin (1) and stemodine (2) synthesis. The adduct (23; R1, R2= SCH2CH2S) was converted via the trione (25) into the ester (27) whose enol ether derivative (28) is a promising precursor to the key aphidicolin intermediate (4).

A Short Stereoselective Synthesis of (±)-Carpamic Acid.

Abstract: The intramolecular N-alkenylnitrone cycloaddition of (9) is the key reaction in an efficient thirteen-step synthesis of carpamic acid (2) from methyl acetoacetate.

A New Synthesis of Eight‐Membered Lactones Containing a 5,6‐Double Bond.

Abstract: Ungesattigte 8-Ring-Lactone (X) erhalt man bei der Claisen-Umlagerung der Vinylketen-acetale (IX).