Barclays will announce early next year a massive restructuring that will likely mean cutting as many as 2,000 jobs in its investment bank, according to sources. The jobs eliminated represent only a small fraction of the British bank’s total investment-banking workforce of roughly 23,000 full-time employees. The move would follow other banks, which have recently shed tens of thousands of jobs, in response to a lousy business climate and pressure regulators have put on banking profits with new rules.