Orthodontic treatment decisions when maxillary central incisors are absent or are of poor prognosis, are discussed. Autotransplantation of mandibular first premolars to the incisor region is suggested as an approach in selected cases. The literature is reviewed, surgical technique described and case selection summarized. Cases are reported where autotransplantation of premolars to the maxillary incisor region has produced good functional and aesthetic results.

Over the past decade, several naturally occurring terpenes containing the tricycl0[6.3.0.O'~~]undecane ring system have been described (1). Representative examples having this unusual bridged spirane moiety include pentalenene (1) (2), isocomene (2) (3), silphinene (3) (4), and structure 4, incorrectly assigned to senoxydene (5). It has been established that 1 is the parent hydrocarbon of the pentalenolactone family of antibiotics (6). The discovery of these compounds has awakened interest in synthetic approaches to various members of the series and several total syntheses of 2 have been described ( I ) , while two methods for each of 1 (2, 7) and 3 (7, 8) have been reported. It may be noted that before the discovery of these natural products the initial synthesis of this ring system was

The known isomerization of the tricyclo[5.3.1.01,5]- to the [6.3.0.01,5]undecane skeleton by β-homoenolization led to examination of 2,9,9-trimethyl-6-methoxymethyltricyclo[5.3.1.01,5]undecanone (6) as a potential precursor for the synthesis of pentalenene, a naturally occurring sesquiterpenoid, utilizing a β-enolate rearrangement as a key step. While the anticipated rearrangement of 6 occurs, it is a minor process. The major rearrangement product arises by generation of a γ-enolate intermediate from a tricyclic enone formed by loss of methanol from 6. This constitutes a new route to [3.3.3]propellanes and provides a third example of γ-enolate rearrangement. Structures of the products were established primarily from their 1H and 13Cmr spectra.

1-Methyl and 1-benzyl-1,2,3,10b-tetrahydro-5,6,8,9-tetramethoxyindeno[1,2,3-ij]isoquinoline have been synthesized from the corresponding 8-phenyl-3,4-dihydro-1(2H)isoquinolinones by treatment with POCl3 under Vilsmeier conditions followed by borohydride reduction. The isoquinolinones were prepared in six steps from 2-(2,3,4-trimethoxyphenyl)-4,4-dimethyl-2-oxazoline. This sequence of reactions provides a new route to dihydro and tetrahydroindeno[1,2,3-ij]isoquinolines.

No abstract